PKG_CHECK_MODULES: Properly check if $pkg_cv_[]$1[]_LIBS works

There is no need to check $pkg_cv_[]$1[]_LIBS works if package check
failed.

config/

	PR binutils/26301
	* pkg.m4 (PKG_CHECK_MODULES): Use AC_TRY_LINK only if
	$pkg_failed = no.

binutils/

	PR binutils/26301
	* configure: Regenerated.

gdb/

	PR binutils/26301
	* configure: Regenerated.