android: Drop the Android.mk build system
Not even Google uses it anymore. For ChromeOS they use meson and for AOSP, they have a custom-rolled blueprint files. We should wean the last few people off of Android.mk and stop maintaining it.
git rm **/Android.mk git rm **/Android.*.mk git rm **/Makefile.sources git rm CleanSpec.mk
Closes: #4487 (closed)