Summary:
We only generate the header dependency (".cc.d") files for files mentioned in "src.mk". When we don't generate them, changes to header dependencies do not cause `make` to recompile the dependent ".o". Then it takes a while for developers (or maybe just me) to realize `make clean` is necessary.
Closes https://github.com/facebook/rocksdb/pull/3876

Differential Revision: D8065389

Pulled By: ajkr

fbshipit-source-id: 0f62eee7bcab15b0215791564e6ab3775d46996b