Revert "Bug 897352 - [gaia build system] Transition to a build_stage for assembling apps" windows bustage

This reverts commit fdd45a31b8372e0f58de51af1856e0a381fe99fa.
Revert "Revert "Merge pull request #17599 from dmarcos/camera-new-features-master""

This reverts commit d9c16d43ea220639982d7aadd2b8e764e9beebe8.

Conflicts:
	build/test/integration/build.test.js
Bug 988118 - Gaia unit test failures on TBPL due to the camera merge