Bug 1866579 - Log revision for depot_tools and chromium src for CaR builds. r=perftest-reviewers,jrmuizel,aglavic

This patch adds minimal code just to keep track of the revisions used
for CaR builds. This will be helpful when trying to find out commits of
interest.

Additionally, in the past we've encountered changes in depot_tools which
caused breakages, so knowing ahead of time the commit(s) to look for
will be helpful.

Differential Revision: https://phabricator.services.mozilla.com/D194654

taskcluster/scripts/misc/build-custom-car.sh

@@ -23,6 +23,10 @@ CUSTOM_CAR_DIR=$PWD
 git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
 export PATH="$PATH:$CUSTOM_CAR_DIR/depot_tools"
 
+# Log the current revision of depot tools for easier tracking in the future
+DEPOT_TOOLS_REV=$(cd depot_tools && git rev-parse HEAD && cd ..)
+echo "Current depot_tools revision: $DEPOT_TOOLS_REV"
+
 # Set up some env variables depending on the target OS
 # Linux is the default case, with minor adjustments for
 # android since it is built with a linux host
@@ -118,6 +122,10 @@ gclient config --name src "https://chromium.googlesource.com/chromium/src.git" -
 
 cd src
 
+# Log the current revision of the chromium src for easier tracking in the future
+CHROMIUM_REV=$(git rev-parse HEAD)
+echo "Current chromium revision: $CHROMIUM_REV"
+
 # Amend gclient file
 if [ "$IS_ANDROID" = true ]; then
   echo "target_os = [ 'android' ]" >> ../.gclient