configure: Fully separate CFLAGS/LDFLAGS between fips and libfips

configure: Fully separate CFLAGS/LDFLAGS between fips and libfips

The top-level program and the underlying library have fundamentally
different requirements. For example, the top-level program needs to
link against libtalloc and libelf but the library does not.

Previously, the necessary flags for both were mixed together in
CONFIGURE_CFLAGS and CONFIGURE_LDFLAGS. This caused the library to
unnecessarily link against libtalloc and libelf, (which in turn caused
problems since the library is compiled as both 32-bit and 64-bit but
the system may not provide both 32- and 64-bit versions of these
libraries).

By splitting things up into separate FIPS_LDFLAGS vs. LIBFIPS_LDFLAGS,
etc. we can keep the dependencies down to what is really required and
eliminate several sprious failure cases.