configure.ac: Fix glib detection
configure.ac: Fix glib detection

When glib is not on the default library search path, the sanity check
failed, because we didn't pick up the LDFLAGS. Do the same with
LDFLAGS like we do with CFLAGS.

Reported-by: Sandor Geller <02e843974d9179bec1c3eb4ff71d53893b0c189f@morganstanley.com>
Signed-off-by: Gergely Nagy <6780fac3b38619ac20422286e4110a70dbba2203@balabit.hu>

algernon/libmongo-client,algernon/libmongo-client,algernon/libmongo-client