scripts: parallel_emerge: Explicit verbose handling.

parallel_emerge is consuming the verbose flag to configure chromite's
logging. parallel_emerge does almost no logging, so it's safe to
assume verbose was meant for emerge.

BUG=b:223433932
TEST=manual parallel_emerge -v

Change-Id: I2c88a5fff3a429443d01919e8dab80cfe57e79fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3937608
Commit-Queue: Alex Klein <saklein@chromium.org>
Commit-Queue: Sergey Frolov <sfrolov@google.com>
Tested-by: Alex Klein <saklein@chromium.org>
Auto-Submit: Alex Klein <saklein@chromium.org>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
diff --git a/scripts/parallel_emerge.py b/scripts/parallel_emerge.py
index bfa9421..ca92421 100644
--- a/scripts/parallel_emerge.py
+++ b/scripts/parallel_emerge.py
@@ -162,6 +162,13 @@
 
     emerge_args.append("--jobs=%s" % parsed_args["jobs"])
 
+    # The -v/--verbose flag gets eaten by the commandline.ArgumentParser to
+    # set the log_level, but it was almost certainly meant to be passed through
+    # to emerge. Check for -v/--verbose directly to avoid coupling this to the
+    # semantics of chromite logging CLI args.
+    if "-v" in argv or "--verbose" in argv:
+        emerge_args.append("--verbose")
+
     emerge_args.append("--rebuild-exclude=chromeos-base/chromeos-chrome")
     for pkg in constants.OTHER_CHROME_PACKAGES:
         emerge_args.append("--rebuild-exclude=%s" % pkg)