Update Git.cs to work on both Windows and Linux runners

The current code uses "Environment.Name" to determine new line delimiter for reading filenames returned by GIT. This causes error for Windows agents/runners because GIT always return with "\n" for new line; whereas for Windows, the "Environment.Name" returned is "\r\n"

tools/code/publisher/Git.cs

@@ -59,7 +59,7 @@ private static async ValueTask<string> GetDiffTreeOutput(CommitId commitId, Dire
 
     private static ImmutableDictionary<CommitStatus, ImmutableList<FileInfo>> ParseDiffTreeOutput(string output, DirectoryInfo baseDirectory)
     {
-        return output.Split(Environment.NewLine, StringSplitOptions.RemoveEmptyEntries)
+        return output.Split("\n", StringSplitOptions.RemoveEmptyEntries)
                      .Choose<string, (CommitStatus Status, FileInfo File)>(line =>
                      {
                          var commitStatus = TryGetCommitStatusFromOutputLine(line);