make 'make clean' work on Solaris, per Gabor Greif comment

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85958 91177308-0d34-0410-b5e6-96231b3b80d8

test/Makefile

@@ -44,6 +44,6 @@ lit.site.cfg: FORCE
 	     $(PROJ_SRC_DIR)/lit.site.cfg.in > $@
 
 clean::
-	@ find -name Output | xargs rm -fr
+	@ find . -name Output | xargs rm -fr
 
 .PHONY: all report clean