scripts: bazel: Set a marker environment variable

Before executing Bazelisk, set CHROMITE_BAZEL_WRAPPER=1 to let it know
that it's invoked via Chromite's Bazel wrapper.

BUG=b:298110833
TEST=chromite/bin/bazel

Change-Id: I1a89c9c7d1511854d93f510b4a4dbde059e2b6a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4907537
Tested-by: Shuhei Takahashi <nya@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Shuhei Takahashi <nya@chromium.org>
diff --git a/scripts/bazel.py b/scripts/bazel.py
index 964794b..702e8b7 100644
--- a/scripts/bazel.py
+++ b/scripts/bazel.py
@@ -157,4 +157,5 @@
     _setup_workspace(opts.project)
 
     bazelisk = _get_bazelisk()
+    os.environ["CHROMITE_BAZEL_WRAPPER"] = "1"
     os.execv(bazelisk, [bazelisk, *bazel_args])