This is an NFC commit to refactor the "load dependent files" parameter from a boolean to an enum value. We want to be able to specify a default, in which case we decide whether or not to load the dependent files based on whether the target is an executable or not (i.e. a dylib).
A second diff will build on top of this to allow the user to specify a value to target -d so we can choose between the default behavior or force (not) loading the dependent files.