This is used to help people easily package experimental versions of the NDK to
test and distribute fixes and improvements. The main idea is to allow external
contributors to play with it in interesting way and share the result easily.
This is used to reduce the number of distributable prebuilt packages
(i.e. linux-x86_64 is not needed anymore).
Also fix build/tools/build-toolchain.sh to properly copy the GPL and LGPL
license files into the generated prebuilt packages.
Also add a .gitignore files to get less spew from 'git status'
Now you need to use the --prebuilt-path=<path> option to specify where to pick up
the prebuilt toolchain tarballs instead, for example:
build/tools/make-release.sh --prebuilt-path=/home/digit/android/ndk
Add also some other options to change the package prefix / release number / etc
