gcc, configure: When checking for basename, use the same process as libiberty [PR119250].

gcc, configure: When checking for basename, use the same process as libiberty [PR119250].

We need the configure result from the decl check for basename() in the GCC
configuration to match that obtained when configuring libiberty or we get
conflicts when <libgen.h> is included in any TU that also includes "system.h"
or "libiberty.h" directly.

	PR other/119250

gcc/ChangeLog:

	* config.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Match the configure test in libiberty when checking
	the basename decl.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>