Support cross system EOL markers

[jrosenb2]

Summary: This loader currently fails when building a package on Windows + the file's within the package have POSIX EOL markers. The root cause is that the loader splits the source file based on the underlying OS EOL marker - the loader is unable to break up the source code into individual lines as it is splitting the source file based on the Windows EOL marker (\r\n) even though the file only contains POSIX EOL markers (\n);

To solve this problem, this pull request splits the file based on either POSIX or Windows EOL markers.

Testing

1. I added test files that contain both Windows + POSIX EOL markers. I ensured the tests failed before this change and passed with this change.
2. I tested this change on a local repo which is checked out on Windows.

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NOTE: This solution was originally suggested in a previous pull request.