api: controller/sysroot.py: Use workon flag

BUG=b:276310194
TEST=CQ

Change-Id: Ie1c26082b6d280ed0e33c585850f556fa53bfe29
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4385954
Tested-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/sysroot.py b/api/controller/sysroot.py
index b19b7ce..0ab7e72 100644
--- a/api/controller/sysroot.py
+++ b/api/controller/sysroot.py
@@ -318,6 +318,9 @@
     # anything.
     dryrun = input_proto.flags.dryrun
 
+    # Allow cros workon packages to build from the unstable ebuilds.
+    workon = input_proto.flags.workon
+
     if not target_sysroot.IsToolchainInstalled():
         cros_build_lib.Die("Toolchain must first be installed.")
 
@@ -336,6 +339,7 @@
         incremental_build=False,
         dryrun=dryrun,
         backtrack=DEFAULT_BACKTRACK,
+        workon=workon,
     )
 
     try: