[XRay][compiler-rt] Add noop patch functions for unsupported arches.

Summary:
Typed event patching is implemented for x86-64, but functions must
be defined for other arches.

Reviewers: dberris, pelikan

Subscribers: nemanjai, javed.absar, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D45749

llvm-svn: 330231