[XRay][Arm] Repair XRay table emission on Arm32 and add tests to identify such problem earlier

Summary:
Emission of XRay table was occasionally disabled for Arm32, but this bug was not then detected because earlier (also by mistake) testing of XRay was occasionally disabled on 32-bit Arm targets. This patch should fix that problem and detect such problems in the future.
This patch is one of a series, see also
- https://reviews.llvm.org/D28623

Reviewers: rengolin, dberris

Reviewed By: dberris

Subscribers: llvm-commits, aemerson, rengolin, dberris, iid_iunknown

Differential Revision: https://reviews.llvm.org/D28624

llvm-svn: 292210