devtool: Create a single file for the build devtool feature

devtool: Create a single file for the build devtool feature

The intention is to have a single file for each devtool feature
so devtool can grow in a modular way. In this direction, this patch creates
build.py, moving all related build features from standard.py to build.py.

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>