Add lld to the test-release.sh script

Building lld is enabled by default, but it can be disabled using the
-no-lld option.

Reviewers: tstellarAMD, rengolin, hans

Reviewed By: hans

Subscribers: grosser, wdng, emaste, llvm-commits

Differential Revision: https://reviews.llvm.org/D29539

llvm-svn: 294102