Symlink gerrit CLI into depot_tools

The "gerrit" tool works just fine outside the SDK.  Let's start
teaching people to use it outside the SDK by putting it in their PATH.

Bug: b:275597798
Change-Id: I79c8090d4e5e205bcac2b763751537791caafe91
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4377791
Auto-Submit: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>

OWNERS

@@ -24,6 +24,7 @@ per-file cbuildbot=file://CROS_OWNERS
 per-file cros=file://CROS_OWNERS
 per-file *cros_python2*=file://CROS_OWNERS
 per-file cros_sdk=file://CROS_OWNERS
+per-file gerrit=file://CROS_OWNERS
 per-file repo=file://CROS_OWNERS
 per-file repo_launcher=file://CROS_OWNERS
 per-file CROS_OWNERS=file://CROS_OWNERS

gerrit

@@ -0,0 +1 @@
+cros