Buildifier overwrites Windows line endings with Unix line endings

I built and ran buildifier on Windows and found that when I run it on .bzl files (e.g. BUILD.bzl) with Windows CRLF line endings, it rewrites the file with Unix line endings. It would be nice if buildifier remembered the original file line endings and outputted the file with those same line endings.

Start by reproducing the issue with buildifier on a .bzl or BUILD.bzl file using Windows CRLF line endings, then trace the formatting and output path that rewrites the file. Done means the formatter preserves the input line-ending style; add or run a regression test covering CRLF input and verify Unix line endings remain supported.

Written by the indexing model from the issue text.