Don't set 'PassBuilder.DisableSimplifyLibCalls'

The simplify-libcalls pass has been removed from LLVM.  Thus
'PassBuilder.DisableSimplifyLibCalls' does not exist anymore.
The disabling/enabling of library call simplifications is
done through the TargetLibraryInfo which is already wired
up in.

git-svn-id: https://llvm.org/svn/llvm-project/dragonegg/trunk@184462 91177308-0d34-0410-b5e6-96231b3b80d8