build: Header file dependency tracking

This patch changes the build system to track header files required to build an
object file. Now you don't need to do make clean if you change a header file!

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

.gitignore

@@ -4,6 +4,7 @@
 .*
 *.o
 *.class
+*.d
 
 #
 # Generated symbolic links

Makefile

@@ -153,6 +153,7 @@ monoburg:
 %.o: %.c
 	$(E) "  CC      " $@
 	$(Q) $(CC) -c $(CFLAGS) $< -o $@
+	$(Q) $(CC) -MM $(CFLAGS) -MT $@ $*.c -o $*.d
 
 %.o: %.S
 	$(E) "  AS      " $@
@@ -213,6 +214,7 @@ clean:
 	$(Q) - rm -f $(PROGRAM)
 	$(Q) - rm -f $(CLASSPATH_CONFIG)
 	$(Q) - rm -f $(OBJS)
+	$(Q) - rm -f $(OBJS:.o=.d)
 	$(Q) - rm -f $(LIBHARNESS_OBJS)
 	$(Q) - rm -f $(ARCH_TEST_OBJS)
 	$(Q) - rm -f arch/$(ARCH)/insn-selector.c
@@ -236,3 +238,5 @@ PHONY += FORCE
 FORCE:
 
 include scripts/build/common.mk
+
+-include $(OBJS:.o=.d)