Attempt to fix macOS build issues

Add `umount` command behavior
Modify to retry 12 times over the course of 240 seconds total
Change `scripts\build\macOS\DMGSetup.scpt` to close DMG when finished.
Improve system detection for setting project name.

Signed-off-by: Emily Mabrey <emabrey@tenacityaudio.org>

scripts/build/macOS/DMGSetup.scpt

@@ -17,6 +17,7 @@ on run argv
               close
               open
               update without registering applications
+              close
         end tell
    end tell
 end run