configure: Various cleanups

Substitute RanlibCmd for consistency, and other configure cleanups that
should have no effect

The other commands are so substituted. Maybe we don't need ranlib at
all, and the configure snippet can be removed all together, but that
can always be done later.

Reviewers: bgamari, hvr, angerman

Reviewed By: bgamari, angerman

Subscribers: rwbarton, thomie, erikd, carter

Differential Revision: https://phabricator.haskell.org/D4286

(cherry picked from commit 8de89305)