configure.ac: make AM_PATH_LIBGCRYPT optional

[michaelolbrich]

Otherwise autogen.sh fails if libgcrypt is not installed. Without this
libgcrypt is a non-optional dependency for tarballs without pre-generated
configure.

[kaysievers]

This is usually done by adding stub lines like:
echo 'AC_DEFUN([AM_PATH_LIBGCRYPT],[:])' > m4/gcrypt.m4

[kaysievers]

This sounds like the proper fix:

On Tue, Jul 7, 2015 at 11:00 AM, Richard Maw richard.maw@codethink.co.uk wrote:

The suggested alternative fix at the time was to submit a patch to make
libgcrypt have a proper pkg-config file, so it can be detected in a
different way, which more easily handles the library not being present.

[keszybz]

This matches what we had in place for gtk-doc and gobject-introspection. Looks like a reasonable workaround until libgcrypt is fixed.

[kaysievers]

This should not be an argument, we removed gtk-doc because it was such a complete mess to handle.

And I see it it the other way around, the one-line-stub seems like the more appropriate workaround until libgcrypt is fixed. Systemd should not work around obvious limitations in other tools, they will never be fixed otherwise.

[kaysievers]

Btw, we also keep "make dist" working, and any "ordinary" Linux machine can create the old school tarball just like we did at release time in the past.

[poettering]

Yes, I am pretty sure that this is something to fix in gcrypt, not work-around like this.