message: Update is_windows() to allow mingw shells
diff: @@ -34,7 +34,7 @@ function cp_external() {
  PLATFORM="$(uname -s | tr 'A-Z' 'a-z')"
  function is_windows() {
  # On windows, the shell script is actually running in msys
  - if [[ "${PLATFORM}" =~ msys_nt* ]]; then
  + if [[ "${PLATFORM}" =~ (mingw64|msys)_nt* ]]; then
  true
  else
  false
  