Add option for -MMD dependencies.

config/rules.mk

@@ -353,6 +353,9 @@ endif
 	+$(LOOP_OVER_DIRS)
 endif
 
+checkout:
+	cd $(topsrcdir); $(MAKE) -f client.mk checkout
+
 clean clobber::
 	rm -rf $(ALL_TRASH)
 	+$(LOOP_OVER_DIRS)
@@ -913,7 +916,14 @@ dependclean::
 -include $(OBJDIR)/depend.mk
 
 endif
+#############################################################################
+# Yet another depend system: -MD
 
+MDDEPENDENCIES		:= $(OBJS:.o=.d)
+
+ifdef MDDEPENDENCIES
+-include $(MDDEPENDENCIES)
+endif
 #############################################################################
 
 -include $(MY_RULES)
@@ -956,7 +966,7 @@ endif
 # Fake targets.  Always run these rules, even if a file/directory with that
 # name already exists.
 #
-.PHONY: all all_platforms alltags boot clean clobber clobber_all export install libs realclean $(OBJDIR) $(DIRS)
+.PHONY: all all_platforms alltags boot checkout clean clobber clobber_all export install libs realclean $(OBJDIR) $(DIRS)
 
 envirocheck::
 	@echo -----------------------------------

configure.in

@@ -632,6 +632,10 @@ MOZ_ARG_WITH_STRING(wrap-malloc,
 [  --with-wrap-malloc-=\$dir location of malloc wrapper library],
   WRAP_MALLOC_LIB=$withval)
 
+MOZ_ARG_ENABLE_BOOL(md,
+[  --enable-md             use compiler-based dependencies ],
+  DEPEND_CFLAGS="-MMD")
+
 AC_SUBST(MOZ_TOOLKIT)
 AC_SUBST(MOZ_UPDATE_XTERM)
 AC_SUBST(MOZ_SECURITY)
@@ -1063,7 +1067,12 @@ dnl End of nspr tests
 dnl ========================================================
 
 dnl Echo the CFLAGS to remove extra whitespace.
-CFLAGS=`echo $WARNINGS_CFLAGS $OPTIMIZE_CFLAGS $GPROF_CFLAGS $CFLAGS`
+CFLAGS=`echo \
+	$WARNINGS_CFLAGS \
+	$OPTIMIZE_CFLAGS \
+	$GPROF_CFLAGS \
+	$DEPEND_CFLAGS \
+	$CFLAGS`
 
 dnl Support for X11 makedepend, if found on the system
 dnl ========================================================