[PATCH] D24799: [XRay] Check in Clang whether XRay supports the target when -fxray-instrument is passed

[Serge Rogatch via cfe-commits]

rSerge added a comment.

In https://reviews.llvm.org/D24799#549442, @dberris wrote:

> What does the error actually look like? Can you add a test for it? It's unclear to me how this would read... for example does it say "XRay for arm is unsupported"?


In the attached picture you can see how the error looks when cross-compiling with Clang from x86_64-Windows host to Thumb-Linux target. 
F2439489: Unsupported XRay target error.jpg <https://reviews.llvm.org/F2439489>
It says

> clang++.exe: error: the clang compiler does not support 'XRay for armv6kz--linux-gnueabihf'


I'll try to add tests.


https://reviews.llvm.org/D24799