When starting Solr built from the master branch on Windows, this is what you see:
The three extra characters, found at the very beginning of the solr.cmd script, are a Unicode BOM, and are invisible to vim, notepad, and notepad++.
The problem does not exist in 6.1.0, but IS present in branch_6x and master.
Using grep to find this character in the entire codebase, I found one other relevant file with a BOM. All others were binary (images, jars, git pack files, etc):