Fix build.h dependencies

For Qt builds, the build.h file is moved to build/build.h. For regular
builds, it is moved to obj/build.h. This allows the Qt build to be done
in a different directory than the source, and without interfering with
other builds.

src/makefile.linux-mingw

@@ -10,7 +10,8 @@ INCLUDEPATHS= \
  -I"$(DEPSDIR)/boost_1_47_0" \
  -I"$(DEPSDIR)/db-4.8.30.NC/build_unix" \
  -I"$(DEPSDIR)/openssl-1.0.0e/include" \
- -I"$(DEPSDIR)"
+ -I"$(DEPSDIR)" \
+ -I"$(CURDIR)"/obj \
 
 LIBPATHS= \
  -L"$(DEPSDIR)/boost_1_47_0/stage/lib" \
@@ -65,14 +66,15 @@ OBJS= \
 
 all: bitcoind.exe
 
-build.h: FORCE
-	@../share/genbuild.sh build.h
+obj/build.h: FORCE
+	../share/genbuild.sh obj/build.h
+version.cpp: obj/build.h
 DEFS += -DHAVE_BUILD_INFO
 
 obj/%.o: %.cpp $(HEADERS)
 	i586-mingw32msvc-g++ -c $(CFLAGS) -o $@ $<
 
-bitcoind.exe: build.h $(OBJS:obj/%=obj/%)
+bitcoind.exe: $(OBJS:obj/%=obj/%)
 	i586-mingw32msvc-g++ $(CFLAGS) -o $@ $(LIBPATHS) $^ $(LIBS)