test-release.sh: Don't use chrpath on Solaris

When trying to run test-release.sh on Solaris 11.4 for 9.0.0 rc4, I failed initially
because Solaris lacks chrpath.  This patch accounts for that and allowed the run to
continue.

Tested on amd64-pc-solaris2.11 and sparcv9-sun-solaris2.11.

Differential Revision: https://reviews.llvm.org/D67484

llvm-svn: 371741