Add BUILD_BROKEN_NINJA_USES_ENV_VARS

See the Changes.md and the paired soong change for more information.

Test: Add BUILD_BROKEN_NINJA_USES_ENV_VARS := OLDPWD
      ALLOW_NINJA_ENV=false m nothing; check out/soong.log
Change-Id: I2167eac52166b513318bc48feb71c9d0b80e5fd4