Support --sysroot with Solaris ld

Support --sysroot with Solaris ld

	* configure.ac (gcc_cv_ld_static_dynamic): Also check stderr for
	$gcc_cv_ld --help output.
	(gcc_cv_ld_demangle): Likewise.
	(gcc_cv_ld_eh_frame_hdr): Likewise.
	(gcc_cv_ld_pie): Likewise.
	(gcc_cv_ld_as_needed): Likewise.  Prefer native forms unless $gnu_ld.
	(gcc_cv_ld_buildid): Likewise.
	(gcc_cv_ld_sysroot): Likewise.
	(ld_bndplt_support): Likewise.
	(ld_pushpopstate_support): Likewise.
	* configure: Regenerate.
	* config/sol2.h [!USE_GLD] (SYSROOT_SPEC): Define.

From-SVN: r249496