Work around a distcc bug where -MMD output isn't copied.

src/makefile.osx

@@ -113,7 +113,7 @@ version.cpp: obj/build.h
 DEFS += -DHAVE_BUILD_INFO
 
 obj/%.o: %.cpp
-	$(CXX) -c $(CFLAGS) -MMD -o $@ $<
+	$(CXX) -c $(CFLAGS) -MMD -MF $(@:%.o=%.d) -o $@ $<
 	@cp $(@:%.o=%.d) $(@:%.o=%.P); \
 	  sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
 	      -e '/^$$/ d' -e 's/$$/ :/' < $(@:%.o=%.d) >> $(@:%.o=%.P); \
@@ -125,7 +125,7 @@ bitcoind: $(OBJS:obj/%=obj/%)
 TESTOBJS := $(patsubst test/%.cpp,obj-test/%.o,$(wildcard test/*.cpp))
 
 obj-test/%.o: test/%.cpp
-	$(CXX) -c $(TESTDEFS) $(CFLAGS) -MMD -o $@ $<
+	$(CXX) -c $(TESTDEFS) $(CFLAGS) -MMD -MF $(@:%.o=%.d) -o $@ $<
 	@cp $(@:%.o=%.d) $(@:%.o=%.P); \
 	  sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
 	      -e '/^$$/ d' -e 's/$$/ :/' < $(@:%.o=%.d) >> $(@:%.o=%.P); \

src/makefile.unix

@@ -125,7 +125,7 @@ version.cpp: obj/build.h
 DEFS += -DHAVE_BUILD_INFO
 
 obj/%.o: %.cpp
-	$(CXX) -c $(xCXXFLAGS) -MMD -o $@ $<
+	$(CXX) -c $(xCXXFLAGS) -MMD -MF $(@:%.o=%.d) -o $@ $<
 	@cp $(@:%.o=%.d) $(@:%.o=%.P); \
 	  sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
 	      -e '/^$$/ d' -e 's/$$/ :/' < $(@:%.o=%.d) >> $(@:%.o=%.P); \
@@ -137,7 +137,7 @@ bitcoind: $(OBJS:obj/%=obj/%)
 TESTOBJS := $(patsubst test/%.cpp,obj-test/%.o,$(wildcard test/*.cpp))
 
 obj-test/%.o: test/%.cpp
-	$(CXX) -c $(TESTDEFS) $(xCXXFLAGS) -MMD -o $@ $<
+	$(CXX) -c $(TESTDEFS) $(xCXXFLAGS) -MMD -MF $(@:%.o=%.d) -o $@ $<
 	@cp $(@:%.o=%.d) $(@:%.o=%.P); \
 	  sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
 	      -e '/^$$/ d' -e 's/$$/ :/' < $(@:%.o=%.d) >> $(@:%.o=%.P); \