sys/cdefs.h missing on musl about efivar

[floppym]

The on_exit function appears to be glibc-specific.
https://www.gnu.org/software/libc/manual/html_node/Cleanups-on-Exit.html

[oxr463]

I took that line out:

sed -i src/compiler.h

This is the only error I see:

efisecdb.c: In function 'main':
efisecdb.c:379:2: warning: implicit declaration of function 'on_exit'; did you mean '_exit'? [-Wimplicit-function-declaration]
  379 |  on_exit(free_actions, &actions);
      |  ^~~~~~~
      |  _exit