targetIsDirectory slipped through the code review of
D6679: Fix T60682: adds macOS alias redirection for directories/rBafb1a64ccb81: Fix T60682: adds macOS alias redirection for directories.
BLI_is_dir exists to check for directory status of a file.

Remove some else-after-returns.

Use r_ prefix for return value arguments, and move it to the end
in the list of arguments.