PR plugins/53126
	* gcc-ar.c (main): If GCC_EXEC_PREFIX is set in env,
	append program name to it and pass that as first argument
	to make_relative_prefix.  Always pass standard_libexec_prefix
	as last argument to make_relative_prefix.  If
	make_relative_prefix returns NULL, fall back to
	standard_libexec_prefix.

From-SVN: r187090