licensing: Enable licensing hook during parallel emerge.

I enabled licensing during the board specific emerge script, but
parallel emerge doesn't use that script, so enable it directly in
parallel emerge.

BUG=chromium:417127
TEST=Local build.

Change-Id: I9fedb6778d6ec7c91c82fc2c0834e62fcb179cf7
Reviewed-on: https://chromium-review.googlesource.com/219641
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
diff --git a/scripts/parallel_emerge.py b/scripts/parallel_emerge.py
index ca768a2..1963632 100644
--- a/scripts/parallel_emerge.py
+++ b/scripts/parallel_emerge.py
@@ -284,6 +284,9 @@
       os.environ["PORTAGE_CONFIGROOT"] = sysroot
       os.environ["PORTAGE_SYSROOT"] = sysroot
       os.environ["SYSROOT"] = sysroot
+      # This enables licensing in gen-package-licenses.sh.
+      # TODO(dgarrett): Remove when it's no longer optional.
+      os.environ["ENABLE_LICENSING"] = "Y"
 
       # Although CHROMEOS_ROOT isn't specific to boards, it's normally setup
       # inside emerge-${BOARD}, so we set it up here for compatibility. It