New comment by pullmoll on void-packages repository

https://github.com/void-linux/void-packages/pull/13005#issuecomment-510799856
Comment:
This is the output of the failing build:
```
make[3]: Entering directory '/builddir/geda-gaf-1.8.2/libgeda/shell'
CPP="aarch64-linux-gnu-cpp" guile-snarf -o shell.x shell.c -DLOCALEDIR=\"/usr/share/locale\" -DHAVE_CONFIG_H -I. -I../..   -I./../include -I../.. -I/usr/include -I../../intl  -Wall   -pthread -I/usr/aarch64-linux-gnu/usr/include/guile/2.0 -I/usr/aarch64-linux-gnu/usr/include/glib-2.0 -I/usr/aarch64-linux-gnu/usr/lib/glib-2.0/include -pthread -I/usr/aarch64-linux-gnu/usr/include/gdk-pixbuf-2.0 -I/usr/aarch64-linux-gnu/usr/include/libmount -I/usr/aarch64-linux-gnu/usr/include/blkid -I/usr/aarch64-linux-gnu/usr/include/glib-2.0 -I/usr/aarch64-linux-gnu/usr/lib/glib-2.0/include
In file included from /usr/include/features.h:474,
                 from /usr/include/unistd.h:25,
                 from shell.c:28:
/usr/include/gnu/stubs.h:7:11: fatal error: gnu/stubs-32.h: No such file or directory
    7 | # include <gnu/stubs-32.h>
      |           ^~~~~~~~~~~~~~~~
compilation terminated.
```
Note the most probably wrong `-I/usr/include` in the `CPPFLAGS` passed to `guile-snarf` for a cross compile.
Perhaps we need a build wrapper for `guile-snarf` to replace `/usr` with `${XBPS_CROSS_BASE}/usr`.