Improve find_and_check_omniidl
Check if the try_run variable is already defined before we run any of the tests.
Renamed the try_run variables to be more meaningful and to avoid collisions as we want them to persist between runs.
Avoid calling the omniidl check when cross compiling without an emulator.
Closes #1049 (closed) and #1060 (closed)
Edited by Thomas Ives