Update configure.ac

[Hello71]

1. the test incorrectly used AC_COMPILE_IFELSE instead of AC_LINK_IFELSE, defeating the purpose of checking -lcrypt.
2. the test did not properly restore LIBS, causing later checks to all fail if libcrypt wasn't found.
3. HAVE_LIBCRYPT only controls whether to use -lcrypt, it is not needed or used in any source files.

[karelzak]

Merged with small changes. Thanks!

[Hello71]

oops, i actually wrote a better commit message but github squashed it at some point. oh well

[Hello71]

your change is not compatible with --as-needed (standard on almost all distros now) or static linking. libraries need to be in LIBS, not LDFLAGS. the similar check for security_get_initial_context will also never succeed on modern distros. fedora example: https://kojipkgs.fedoraproject.org//packages/util-linux/2.37/2.fc35/data/logs/x86_64/build.log "checking for security_get_initial_context... no". yet https://kojipkgs.fedoraproject.org//packages/util-linux/2.37/2.fc35/data/logs/x86_64/root.log says "DEBUG util.py:446: libselinux x86_64 3.2-2.fc35 build 83 k" which does have security_get_initial_context: https://github.com/SELinuxProject/selinux/blob/libselinux-3.2/libselinux/src/get_initial_context.c

[karelzak]

Oh, that's a stupid thing. It's really useless with --as-needed. Fixed.

Thanks!

[asavah]

@karelzak commit 75cba8d breaks crypt() detection.

ncurses and other libs detection seems to work fine

EDIT: scratch that, I haven't had my git tree fully updated, 75cba8d actually fixes the issue introduced by an earlier commit.
Sorry for the noise,