There are a number of files in the installation directory that we open that need to be opened early and then accessed only via file descriptors.

It would be nice to have a general solution to this problem, where we would automatically pre-open everything that we might need later, but this may not actually be necessary. There just aren't that many non-library files in the installation directory that Firefox opens. This makes it feasible that we could simply enumerate the files of concern and individually make sure that we open handles to them sufficiently early that we could ensure that we get the right version when we need it. Testing would ensure that we don't regress this.