This adds the test I was using when testing 60d67dc8.
* testsuite/ld-elfweak/alias.c,
* testsuite/ld-elfweak/alias.dat,
* testsuite/ld-elfweak/aliasmain.c,
* testsuite/ld-elfweak/weakref1.c,
* testsuite/ld-elfweak/weakref2.c: New test.
* testsuite/ld-elfweak/elfweak.exp: Run it. Don't return on fails,
attempt other tests.
