Update android build

[palango]

The current android build recommends the following changes:

WARNING:__main__:make_standalone_toolchain.py is no longer necessary. The
$NDK/toolchains/llvm/prebuilt/linux-x86_64/bin directory contains target-specific scripts that perform
the same task. For example, instead of:

    $ python $NDK/build/tools/make_standalone_toolchain.py \
        --arch x86 --api 21 --install-dir toolchain
    $ toolchain/bin/clang++ src.cpp

Instead use:

    $ $NDK/toolchains/llvm/prebuilt/linux-x86_64/bin/i686-linux-android21-clang++ src.cpp

Maybe helpful: https://gist.github.com/pgp/f4c3bbf67821bd131812a8658f016fbc

[palango]

Duplicate of #22