CI: Use the same logic for prerelease suffix as during build

Author: cameel

.circleci/config.yml

@@ -187,10 +187,13 @@ commands:
       - run:
           name: Store prerelease suffix
           command: |
-            if [[ -n $CIRCLE_TAG ]]; then
-              echo -n > prerelease.txt;
+            if [[ -n "$CIRCLE_TAG" || -n "$FORCE_RELEASE" ]]; then
+                echo -n > prerelease.txt
             else
-              date -u +"nightly.%Y.%-m.%-d" > prerelease.txt;
+                # Use last commit date rather than build date to avoid ending up with builds for
+                # different platforms having different version strings (and therefore producing different bytecode)
+                # if the CI is triggered just before midnight.
+                TZ=UTC git show --quiet --date="format-local:%Y.%-m.%-d" --format="nightly.%cd" > prerelease.txt
             fi
 
   install_and_check_minimum_requirements: