Make ghc-api cleaning less aggressive.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

testsuite/tests/ghc-api/Makefile

@@ -5,15 +5,18 @@ include $(TOP)/mk/test.mk
 clean:
 	rm -f *.o *.hi
 
-T6145: clean
+T6145:
+	rm -f T6145.o T6145.hi
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -v0 -package ghc T6145
 	./T6145 "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`"
 
-T8639_api: clean
+T8639_api:
+	rm -f T8639_api.o T8639_api.hi
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -v0 -package ghc T8639_api
 	./T8639_api "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`"
 
-T8628: clean
+T8628:
+	rm -f T8628.o T8628.hi
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -v0 -package ghc T8628
 	./T8628 "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`"