Remove all_modules's dependency on keymaps validation.

With this we won't try to run validatekeymaps.exe when you run
"USE_MINGW=1 mma".
Also it seems it's too much to run the validation for every mma/mmma.
Validation in just platform build (droidcore) should be enough.

Change-Id: I22431009d4c2dd765bbd14b24eb5c8729b53d6c1