Needs too much CPU, slows down Ubuntu 18.04 boot

[TheAssassin]

Original issue: AppImage/AppImageKit#744

[probonopd]

Would http://libevent.org/ be useful here?

[TheAssassin]

libuv is IMO better. But that won't speed up recursively searching all directories and touching all files.

[probonopd]

But that won't speed up recursively searching all directories and touching all files.

That's not my issue at all. The issue is that the caches get rebuilt whenever we copy desktop files and icons into place, which is "all the time" rather than "once every X seconds" or "after there was no AppImage processed for X seconds".

In other words, I believe that fixing #12 will solve this issue in large part.