[XRay] ARM 32-bit no-Thumb support in compiler-rt

This is a port of XRay to ARM 32-bit, without Thumb support yet.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

https://reviews.llvm.org/D23931 (LLVM)
https://reviews.llvm.org/D23932 (Clang test)

Differential Revision: https://reviews.llvm.org/D23933

llvm-svn: 281971