have-lib: ‘additional_libdir’ set to ‘PREFIX/lib64’

[Ludovic Courtès]

Hello,

When passed ‘--with-PACKAGE-prefix=/p’, ‘AC_LIB_LINKFLAGS_BODY’
deduces ‘additional_libdir=/p/lib64’ on x86_64.

This doesn’t work on NixOS which doesn’t (quite) support multilib, and
where libs are to be found under ‘/p/lib’.  Unfortunately, this leads
‘AC_LIB_LINKFLAGS_BODY’ to ignore the ‘/p’ prefix altogether, both for
includes and libs (it ends up in the “Didn't find the library” case).

A simple fix would be to add a ‘--with-PACKAGE-lib’ (and optionally
‘--with-PACKAGE-include’) option.  A better fix may be to have
“additional_libdir="/p/lib64 /p/lib"” or similar.

What do you think?

Thanks,
Ludo’.