Make sync script work correctly with Windows-style newlines

I'm almost certain nobody is actually running this script on Windows,
but the tests for it do run during `nmake check`, and they fail at least
on my git configuration.

The $ anchor doesn't match \r\n with git's -E regex matching, so we need
to add \r? to gobble the carriage-return up too if needed.

tool/sync_default_gems.rb

@@ -489,7 +489,9 @@ def message_filter(repo, sha, input: ARGF)
   def commits_in_ranges(gem, repo, default_branch, ranges)
     # If -a is given, discover all commits since the last picked commit
     if ranges == true
-      pattern = "https://github\.com/#{Regexp.quote(repo)}/commit/([0-9a-f]+)$"
+      # \r? needed in the regex in case the commit has windows-style line endings (because e.g. we're running
+      # tests on Windows)
+      pattern = "https://github\.com/#{Regexp.quote(repo)}/commit/([0-9a-f]+)\r?$"
       log = IO.popen(%W"git log -E --grep=#{pattern} -n1 --format=%B", &:read)
       ranges = ["#{log[%r[#{pattern}\n\s*(?i:co-authored-by:.*)*\s*\Z], 1]}..#{gem}/#{default_branch}"]
     end