* acinclude.m4 (GLIBCPP_CHECK_PCH): Only set glibcpp_PCHFLAGS if
	.gch compilation works.
	* aclocal.m4, configure: Regenerate.
	* testsuite_flags.in (--build-cxx): Use glibcpp_PCHFLAGS to
	initialize PCHFLAGS.

From-SVN: r67515