Fix run-one-test so that it runs elf tests

The `test' make target passes a trailing slash in the subdir argument.  This
does not play well with elf/rtld-Rules which looks for `elf' without any
trailing slash, and therefore doesn't find a match when running an elf test
individually.  This commit removes the trailing slash from the invocation.

Reviewed-by: DJ Delorie <dj@redhat.com>

Makefile

@@ -691,6 +691,6 @@ iconvdata/% localedata/% po/%: FORCE
 .PHONY: test
 test :
 	@-rm -f $(objpfx)$t.out
-	$(MAKE) subdir=$(dir $t) -C $(dir $t) ..=../ $(objpfx)$t.out
+	$(MAKE) subdir=$(patsubst %/,%,$(dir $t)) -C $(dir $t) ..=../ $(objpfx)$t.out
 	@cat $(objpfx)$t.test-result
 	@cat $(objpfx)$t.out