make the clean_libraries target work, so you can "make clean" in libraries/

ghc.mk

@@ -894,10 +894,14 @@ CLEAN_FILES += utils/ghc-pwd/ghc-pwd.hi
 CLEAN_FILES += utils/ghc-pwd/ghc-pwd.o
 CLEAN_FILES += libraries/bootstrapping.conf
 
-clean : clean_files
+clean : clean_files clean_libraries
+
 .PHONY: clean_files
 clean_files :
 	$(RM) $(CLEAN_FILES)
+
+.PHONY: clean_libraries
+clean_libraries:
 	$(RM) -r $(patsubst %, libraries/%/dist, $(PACKAGES) $(PACKAGES_STAGE2))
 	$(RM) -r $(patsubst %, libraries/%/dist-install, $(PACKAGES) $(PACKAGES_STAGE2))
 	$(RM) -r $(patsubst %, libraries/%/dist-boot, $(PACKAGES) $(PACKAGES_STAGE2))

rules/build-package.mk

@@ -45,10 +45,8 @@ $(call all-target,$1,all_$1_$2)
 $(call clean-target,$1,$2,$1/$2)
 # This give us things like
 #     all_libraries: all_libraries/base_dist-install
-#     clean_libraries: clean_libraries/base_dist-install
 ifneq "$$($1_$2_GROUP)" ""
 all_$$($1_$2_GROUP): all_$1_$2
-clean_$$($1_$2_GROUP): clean_$1_$2
 endif
 
 distclean : clean_$1_$2_config