build: use required platform in android-configure

The introduction of libuv 1.6.0 broke the android-configure script by
not specifying the correct platform. uv_os_homedir uses getpwuid_r
which was not made public until API level 21 on android.

The regression was introduced in a804026c...b5cd2f09

PR-URL: https://github.com/nodejs/node/pull/2501


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>