Fix support for UNC paths in Powershell executor
Fixes #3761 (closed). For my particular case, with a working directory on an UNC path, builds work with the commit and do not work without it (failing as described in #3761 (closed)).
Fixes #3761 (closed). For my particular case, with a working directory on an UNC path, builds work with the commit and do not work without it (failing as described in #3761 (closed)).