artifacts: Pass sysroot instead of buildroot.

BuildEbuildLogs... conflates buildroot with sysroot.
Adjust accordingly.

TEST=./run_tests
BUG=chromium:949566

Change-Id: I8cc2891d34cbb4abef0ed231332055a9fd096621
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1558771
Tested-by: Evan Hernandez <evanhernandez@chromium.org>
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
diff --git a/api/controller/artifacts.py b/api/controller/artifacts.py
index 51e2454..7d68206 100644
--- a/api/controller/artifacts.py
+++ b/api/controller/artifacts.py
@@ -145,7 +145,10 @@
   """
   target = input_proto.build_target.name
   output_dir = input_proto.output_dir
-  build_root = constants.SOURCE_ROOT
+
+  # commands.BuildEbuildLogsTarball conflates "buildroot" with sysroot.
+  # Adjust accordingly...
+  build_root = os.path.join(constants.SOURCE_ROOT, 'chroot', 'build')
 
   # TODO(saklein): Replace with a chromite/service implementation.
   archive = commands.BuildEbuildLogsTarball(build_root, target, output_dir)