re PR bootstrap/49173 (No rule to make target `../../../../work/libgcc/../gcc/libgcc-std.ver', needed by `libgcc.map'.)

	PR bootstrap/49173
	* config/t-slibgcc-darwin (SHLIB_MAPFILES): Look for
	libgcc-std.ver in the build directory.
	* config/s390/t-linux (SHLIB_MAPFILES): Likewise.
	* config/sh/t-linux (SHLIB_MAPFILES): Likewise.

From-SVN: r174321