configure.ac: fix static build

configure.ac: fix static build

For static build, some extra LDFLAGS may be needed.

Using PKG_CHECK_MODULES instead of AC_CHECK_LIB for librairy detection
allows to get all these flags. Then, the LIBS variable can be extended
with everything that is needed.

So, use PKG_CHECK_MODULES for popt and uuid detection; which both depend
on libintl.

This changes fixes build failures triggered with Buildroot, e.g.:
  http://autobuild.buildroot.net/results/0f1/0f1e015a0c5a5ac2beeb5011d31a1e0058a32a0d/build-end.log

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>