Makefile: Remove chrpath workaround for bug in cabal,  which is no longer
needed.

https://github.com/haskell/cabal/issues/2717 says it uses RUNPATH instead
of RPATH now, but I don't even see that for statically linked libraries;
the bug with that appears to be fixed.

cabal-install version 1.24.0.2
compiled using version 1.24.2.0 of the Cabal library

I left the rpath removal using otool on OSX because those straight up
broke the linker, and I don't know if the OSX autobuilder is updated to
a new enough cabal to not need it.

This commit was sponsored by Ewen McNeill on Patreon.