Update lit config for ld.lld command to match "ld\.lld" instead of trying to...

Update lit config for ld.lld command to match "ld\.lld" instead of trying to match respective regex. (It was able to work with ld-lld and ld1lld as well)

Differential Revision: https://reviews.llvm.org/D59962

llvm-svn: 357218