ld: Support LD_UNDER_TEST environment variable

Support LD_UNDER_TEST environment variable to test a different linker.
Issue an error if LD_UNDER_TEST isn't an absolute full path.

	* testsuite/config/default.exp: If LD_UNDER_TEST environment
	variable exists, set ld and LD to it and set up tmpdir/ld/ld.
	Issue an error if LD_UNDER_TEST isn't an absolute full path.
1 file changed