In the pure `ld` case, we weren't actually parsing `RPATH` arguments separately as we
do for `ccld`. Fix this by adding *another* nested case statement for raw `RPATH`
parsing.
There are now 3 places where we deal with `-rpath` and friends, but I don't see a great
way to unify them, as `-Wl,`, `-Xlinker`, and raw `-rpath` arguments are all ever so
slightly different.
Also, this Fixes ordering of assertions to make `pytest` diffs more intelligible.
The meaning of `+` and `-` in diffs changed in `pytest` 6.0 and the "preferred" order
for assertions became `assert actual == expected` instead of the other way around.
Signed-off-by: Todd Gamblin <tgamblin@llnl.gov>