Building gnupg2 tests is broken on musl libc

[Greg Troxel]

Pierre Labastie via Gnupg-devel <gnupg-devel at gnupg.org> writes:

> Commit 86baca6e62b33 has introduced the use of the "time_t" type in
> tests/gpgscm/scheme.c. The problem is that using this type requires to
> #include <time.h>. It happens that with glibc the type is also defined
> when including <stdlib.h>, but this is not portable (all man pages
> about time_t tell to include time.h).

Not just man pages, but POSIX:

  https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/time.h.html