system: load <libpath>/../pkg if <libpath>/pkg doesn't exist but <libpath>/../pkg does

[illwieckz]

Load <libpath>/../pkg if <libpath>/pkg doesn't exist but <libpath>/../pkg does.

This to workaround the fact most file browsers will create a subfolder when extracting an archive that doesn't contain one.

This makes Unvanquished_0.56.0/linux-amd64/daemon load Unvanquished_0.56.0/pkg the same way Unvanquished_0.56.0/daemon loads Unvanquished_0.56.0/pkg.

[illwieckz]

Using FS::RawPath::ListFiles() is overkill but we don't have yet a dedicated function to test that a directory exists.

[slipher]

I'm against it. Going into .. to look for resources seems like a fishy and insecure design.

Curiously, this could cause a build in Unvanquished/build to automatically find the repository's pkg/. This could seem "convenient" but I think it is a bad idea. I don't want stuff to unpredictably change behavior based on how you choose the build dir. And testing with only released assets is an often desired use case.