[Merge Request] Enable q3map2 out-of-tree compilation

Hi, if I generate bsp or lightmaps from a .map or minimap and navmeshes from a .bsp, the files are written in the same directory the source is.

There is multiple issues to that.

• It means a build script must move generated assets right after the build if their intended places are not in the maps/ directory.
• q3map2 does not allow out-of-tree build, the only way to not mess a source directory is to copy it in a temporary directory before building.

Using an -outpath option (or another name you prefer) will fix these two issues.