Make configure.ac POSIX compliant

Configure scripts need to be runnable with a POSIX-compliant /bin/sh. Replace
== comparison operator (bashism) with = (POSIX) to fix errors:

configure: WARNING: tcpd.h not found
./configure: 8453: test: X: unexpected operator
checking that generated files are newer than configure... done

Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Jan Kara <jack@suse.cz>
1 file changed