Rename build.ninja with product name

Current build.ninja does not contain any product name, while other ninja
files (such as combined ninja) do. This change adds product name to the
build.ninja so it can be separated over multiple lunch targets

Bug: 277029044
Test: build succeeded and checked if out/soong/build.ninja has been
renamed

Change-Id: I16dc71f829fd76f01b98da0d509a8e0ef6f62fa9