I've switched all the build server configs to using TARGET_PRODUCT /
TARGET_BUILD_VARIANT and explicit goals instead.
Remove tools/check_builds.sh which relied on this, but hasn't been
touched in a long time.
Test: m PRODUCT-test
Test: treehugger
Change-Id: If5f8c714567b33aeb38223c176ca24ea649eb57d
For the envsetup.sh variables that should not be used in makefiles
(since they're not explicitly set up, and won't be available on the
build servers), mark them as deprecated.
Rework our documentation to have a landing page, and create a "Changes"
section where we can record changes like these. At some point I may go
and backfill some recent work.
Test: build/soong/build_test.bash
Change-Id: I54b9294ddf270245afdb58d17150db8098584e8a
