We were emulating this for proto files, standardize it and make the
other generators use it as well.
Test: Compare out/soong/build.ninja before/after change
Test: mmma -j system/tools/hidl
Change-Id: I1888c7b981749060a398387bbb9b481270bf6d75
.proto files are translated to .pb.cc and .pb.h files, which are then
compiled normally.
Bug: 32286026
Test: mmma -j system/extras/perfprofd
Change-Id: I538071424d667aacf35b4b8bfebe217f5f092726