Export env vars before lunching and building.

This is necessary for vars that are checked in early-parse makefiles
like [device].mk or BoardConfig.mk.

Bug: 201683015
Test: Use build_android_target.sh within NSJail, observe that build
      command vars are exported to the environment and used by the
      build's device.mk file.
Change-Id: Ie6222ac977cb3faddaa3a8f2091cb32fb3479a02
1 file changed