New comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/30155#issuecomment-821775680

Comment:
```
 aarch64-linux-musl-cpp -I. -I..   _gpg-error.def.h | \
  grep -v '^#' >gpg-error.def
rm _gpg-error.def.h
echo "/*dummy*/" > mkw32errmap.map.c
cc -O2 -pipe  \
 -I. -I. -o mkerrcodes ./mkerrcodes.c
./mkerrcodes | gawk -f ./mkerrcodes2.awk >code-from-errno.h
if test -f lock-obj-pub.native.h; then rm lock-obj-pub.native.h; fi
./mkheader --cross       \
                   aarch64-unknown-linux-musl  ./gpg-error.h.in \
                   ../config.h 1.42 0x012a00 >gpg-error.h
./gpg-error.h.in:508: error including `./syscfg/lock-obj-pub.linux-musl.h': No such file or directory
```

the build broke for our musl cross targets, it seems.