If the expected arch directory doesn't exist, give up and don't specify arch at
all. Currently it expands to '*' which fails.
[slightly modified by apenwarr]
Just kidding. This is a squash of a whole bunch of unlabeled temporary
commits that I produced over the last couple of weeks while writing a UI
for MacOS while riding on airplanes and sitting in airports.
So long, batch of useless commits!