Allow adding to the file prefix list taken from the env

[zwimer]

This can be useful when the library loads before the file paths are known.

For example, if this is being used in a library and the path information is only known by the parent process; without this the library would (by default) before main, before the main process could give this information.

In my use case, this is part of a native module to another programming language, the module is loaded when the native program loads, however, so the program does not have any time to inform backward of where the files.

[zwimer]

This message is to keep the PR from going stale.

[zwimer]

Is there anything I can do to help get this merged?

[zwimer]

@bombela What should I do to get this merged?

[bombela]

Just me being lazy, sorry. Thank you for your patience, your time, and your work.