Documentation clarification: -l is useable in require statements, but -L and -I are not

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Summary of Problem

According to C interop docs you can use -L and -I flags in require statements to indicate non-standard header and library search directories, but on main (cb81008e74565fa) for

module myFoo {
  use CTypes;
  require "-L../../path/to/userspace/lib";
  require "-luserlib";
  ...
}

I am getting

wrapper.chpl:4: error: file '-L../../path/to/userspace/lib' does not have a recognized suffix

It does not complain about -l statements, though the linker obviously fails later because it doesn't know where to look for them..

As an aside, is there/should there be support for --isystem?