New issue by ericonr on void-packages repository

https://github.com/void-linux/void-packages/issues/32549

Description:
Build `libcap` for cross, it's been spotted happening with `arm*` and aarch64, at least, probably happens for all cross situations. Happened repeatedly on builders at one moment, but can't always be reproduced.

From https://github.com/void-linux/void-packages/pull/32309#issuecomment-894884367 :

> There's something wonky in the build, https://build.voidlinux.org/builders/armv7l-musl_builder/builds/35184/steps/shell_3/logs/stdio

```
=> libcap-2.52_1: running do_install ...
make -C libcap install
make[1]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/capability.h /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libcap.pc /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libcap.pc
install -m 0644 libcap.a /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/libcap.a
make install-static-psx
make[2]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/psx_syscall.h /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libpsx.pc /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libpsx.pc
install -m 0644 libpsx.a /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/libpsx.a
make[2]: Leaving directory '/builddir/libcap-2.52/libcap'
make install-shared
make[2]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/capability.h /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libcap.pc /destdir/armv7l-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libcap.pc
objcopy --dump-section .interp=/dev/stdout empty > loader.txt
objcopy: Unable to recognise the format of the input file `empty'
make[2]: *** [Makefile:108: loader.txt] Error 1
make[2]: Leaving directory '/builddir/libcap-2.52/libcap'
make[1]: *** [Makefile:153: install] Error 2
make[1]: Leaving directory '/builddir/libcap-2.52/libcap'
make: *** [Makefile:12: install] Error 2
```

From https://termbin.com/3qvw (obtained from IRC):

```
=> libcap-2.53_1: running do_install ...
make -C libcap install
make[1]: Entering directory '/builddir/libcap-2.53/libcap'
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib
install -m 0644 include/sys/capability.h /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
install -m 0644 libcap.pc /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig/libcap.pc
install -m 0644 libcap.a /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/libcap.a
make install-static-psx
make[2]: Entering directory '/builddir/libcap-2.53/libcap'
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib
install -m 0644 include/sys/psx_syscall.h /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
install -m 0644 libpsx.pc /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig/libpsx.pc
install -m 0644 libpsx.a /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/libpsx.a
make[2]: Leaving directory '/builddir/libcap-2.53/libcap'
make install-shared
make[2]: Entering directory '/builddir/libcap-2.53/libcap'
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib
install -m 0644 include/sys/capability.h /destdir/aarch64-linux-gnu/libcap-2.53/usr/include/sys
install -m 0644 libcap.pc /destdir/aarch64-linux-gnu/libcap-2.53/usr/lib/pkgconfig/libcap.pc
gcc -fstack-clash-protection -D_FORTIFY_SOURCE=2 -O2 -pipe -march=armv8-a   -I/usr/aarch64-linux-gnu/usr/include -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -fPIC -I/builddir/libcap-2.53/libcap/../libcap/include/uapi -I/builddir/libcap-2.53/libcap/../libcap/include -DLIBRARY_VERSION=\"libcap-2.53\" -DSHARED_LOADER=\"/lib/ld-linux-aarch64.so.1\" -c execable.c -o cap_magic.o
cc1: error: bad value ('armv8-a') for '-march=' switch
cc1: note: valid arguments to '-march=' switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client icelake-server cascadelake tigerlake cooperlake bonnell atom silvermont slm goldmont goldmont-plus tremont knl knm x86-64 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 btver1 btver2 native
make[2]: *** [Makefile:111: cap_magic.o] Error 1
make[2]: Leaving directory '/builddir/libcap-2.53/libcap'
make[1]: *** [Makefile:153: install] Error 2
make[1]: Leaving directory '/builddir/libcap-2.53/libcap'
make: *** [Makefile:12: install] Error 2
```

Local build:

```
=> libcap-2.52_1: running do_install ...
make -C libcap install
make[1]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/capability.h /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libcap.pc /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libcap.pc
install -m 0644 libcap.a /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/libcap.a
make install-static-psx
make[2]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/psx_syscall.h /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libpsx.pc /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libpsx.pc
install -m 0644 libpsx.a /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/libpsx.a
make[2]: Leaving directory '/builddir/libcap-2.52/libcap'
make install-shared
make[2]: Entering directory '/builddir/libcap-2.52/libcap'
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig
mkdir -p -m 0755 /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib
install -m 0644 include/sys/capability.h /destdir/arm-linux-musleabihf/libcap-2.52/usr/include/sys
install -m 0644 libcap.pc /destdir/arm-linux-musleabihf/libcap-2.52/usr/lib/pkgconfig/libcap.pc
gcc -fstack-clash-protection -D_FORTIFY_SOURCE=2 -O2 -pipe -march=armv6 -mfpu=vfp -mfloat-abi=hard   -I/usr/arm-linux-musleabihf/usr/include -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -Dlinux -Wall -Wwrite-strings -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -g  -fPIC -I/builddir/libcap-2.52/libcap/../libcap/include/uapi -I/builddir/libcap-2.52/libcap/../libcap/include -DLIBRARY_VERSION=\"libcap-2.52\" -DSHARED_LOADER=\"/lib/ld-musl-armhf.so.1\" -c execable.c -o cap_magic.o
gcc: error: unrecognized command-line option '-mfpu=vfp'
gcc: error: unrecognized command-line option '-mfloat-abi=hard'
make[2]: *** [Makefile:111: cap_magic.o] Error 1
make[2]: Leaving directory '/builddir/libcap-2.52/libcap'
make[1]: *** [Makefile:153: install] Error 2
make[1]: Leaving directory '/builddir/libcap-2.52/libcap'
make: *** [Makefile:12: install] Error 2
```

The existence of build steps during do_install seems like a clue as to what might be the issue.