Use c and cpp objects for gcov.

Instead of using all_objects and translating .o to .gcno, use
cpp_objects, gen_cpp_objects, c_objects, gen_c_objects, objc_objects,
and objcpp_objects. Fixes bug with .s files breaking coverage builds.

Bug: 35843991
Test: lunch sailfish-userdebug && make -j60 NATIVE_COVERAGE=true
COVERAGE_PATHS="vendor/google_devices/marlin/proprietary/mm-camera/mm-camera2"
Change-Id: Ib2f8eef889f075ec82f79d8c3ae0fe31962b653d