stop clang -MM stripping path for object files

I have a subdirectory with source in it. I would like clang++ -I. -MM path/to/source.cpp to give me the following output:

path/to/source.o: path/to/source.cpp path/to/source.h

Instead it gives me this:

source.o: path/to/source.cpp path/to/source.h

This seems like it would require me making Makefiles to list dependencies for every single source directory for my project?