Add --windowed argument to pyinstaller for OS X

bin/build-dist

@@ -22,6 +22,12 @@ pyinstaller_args+="--hidden-import gi.repository.Gtk "
 # mac and windows build seem to miss wx import
 pyinstaller_args+="--hidden-import wx "
 
+# We need to use the precompiled bootloader linked with graphical Mac OS X
+# libraries if we develop a GUI application for Mac:
+if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+    pyinstaller_args+="--windowed "
+fi
+
 # This lets pyinstaller see inkex.py, etc.
 pyinstaller_args+="-p inkscape-0.92.3/share/extensions "