calc_release_version.py reports the wrong version if on a non-release non-master branch. This was the cause of abi-compliance-check always failing on patches from GitHub PRs (because they were running from non-master branches).

Additionally, calc_release_version.py run from a release non-master branch, uses the --merged option in git, which requires a newer version of git than we have on all variants. Example of a failing task on the r1.17 evergreen project.

As a temporary workaround, I've hardcoded VERSION_CURRENT in the evergreen config.