nitg: extract toolchain methods into a new ToolChain class

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitg: refactor the ToolChain class by adding an abstract super class

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitg: intro the platform concept

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
android: adds support for the android platform

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: minimal test for compilation to android

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: skip android related test in niti

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>