modules: remove .cache.mk on make clean

Remove .cache.mk inside vmmon-only and vmnet-only when executing
"make clean". This file can cause issues when upgrading gcc as make will
still look for includes inside older gcc includes directory.

File .cache.mk with cache of generated variables was created by build since
kernel v4.15-rc1, commit 3298b690b21c ("kbuild: Add a cache for generated
variables") until the feature was removed in v4.18-rc1, commit e08d6de4e532
("kbuild: remove kbuild cache").

vmmon-only/Makefile.kernel

@@ -31,7 +31,7 @@ $(DRIVER)-y := $(subst $(SRCROOT)/, , $(patsubst %.c, %.o, \
 		$(SRCROOT)/bootstrap/*.c)))
 
 clean:
-	rm -rf $(wildcard $(DRIVER).mod.c $(DRIVER).ko .tmp_versions \
+	rm -rf $(wildcard $(DRIVER).mod.c $(DRIVER).ko .tmp_versions .cache.mk \
 		Module.symvers Modules.symvers Module.markers modules.order \
 		$(foreach dir,linux/ common/ vmcore/ bootstrap/ \
 		./,$(addprefix $(dir),.*.cmd .*.o.flags *.o)))

vmnet-only/Makefile.kernel

@@ -32,6 +32,6 @@ $(DRIVER)-y := driver.o hub.o userif.o netif.o bridge.o procfs.o smac_compat.o \
 ####
 
 clean:
-	rm -rf $(DRIVER).o $(DRIVER).mod.o $(DRIVER).mod.c $(DRIVER).ko \
+	rm -rf $(DRIVER).o $(DRIVER).mod.o $(DRIVER).mod.c $(DRIVER).ko .cache.mk \
 	       .tmp_versions Module.symvers Modules.symvers Module.markers \
 	       modules.order $($(DRIVER)-y) .*.cmd .*.o.flags