How to adding pathes to dependencies in rules of `.d` files

[ljh]

Hi community,

I managed to do out-of-source build.

I use `CPPFLAGS += -MMD -MP` to generate `.d` files. 
The `.d` files and the source files are not in the same directory now.
`make` addes path the the target `.o` part, 
but not the prerequisites parts `.c`, `.h`.

So, the rules in `.d` files will not take effect.
Now, If I `touch` my `.h` files, it will not re-build the source files.

Is there a way to inform `make` to add path to the prerequisites too?

Thanks

$ cat build/build/foo/foo.d 
/home/ljh/Documents/make/src/build/build/foo/foo.o: foo.c foo.h
foo.h:
$ 

$ tree --charset C
.
|-- build
|   `-- build
|       |-- foo
|       |   |-- foo
|       |   |-- foo.d
|       |   |-- foo.o
|       |   `-- libfoo.so
|       `-- main
|           |-- main
|           |-- main.d
|           `-- main.o
|-- foo
|   |-- foo.c
|   |-- foo.h
|   `-- Makefile
|-- main
|   |-- main.c
|   `-- Makefile
`-- Makefile

$