remove .o and .hi files beforehand

testsuite/tests/ghc-regress/indexed-types/should_compile/Makefile

@@ -3,5 +3,6 @@ include $(TOP)/mk/boilerplate.mk
 include $(TOP)/mk/test.mk
 
 NewTyCo:
+	$(RM) NewTyCo1.o NewTyCo1.hi NewTyCo2.o NewTyCo2.hi
 	$(TEST_HC) -c NewTyCo1.hs
 	$(TEST_HC) -c NewTyCo2.hs

testsuite/tests/ghc-regress/typecheck/should_compile/Makefile

@@ -3,6 +3,7 @@ include $(TOP)/mk/boilerplate.mk
 include $(TOP)/mk/test.mk
 
 tc173:
+	$(RM) Tc173a.o Tc173a.hi Tc173b.o Tc173b.hi
 	$(TEST_HC) -c -fglasgow-exts -XUndecidableInstances -XOverlappingInstances Tc173a.hs
 	$(TEST_HC) -c -fglasgow-exts -XUndecidableInstances -XOverlappingInstances Tc173b.hs