Figure out if XRAY is still usable

[surovic]

I'm not sure. Since we built a modified version of the whole compiler-rt previously, we did have XRAY included in it. The compiler-rt excerpt from this PR doesn't have it included. Theoretically it should be possible to link against an apt installed version of compiler-rt but I haven't tried that.

Originally posted by @surovic in #6517 (comment)