Summary:
Adds a CMake check for whether the compiler used to build the XRay
library supports XRay-instrumentation. If the compiler we're using does
support the `-fxray-instrument` flag (i.e. recently-built Clang), we
define the XRAY_NEVER_INSTRUMENT macro that then makes sure that the
XRay runtime functions never get XRay-instrumented.
This prevents potential weirdness involved with building the XRay
library with a Clang that supports XRay-instrumentation, and is
attempting to XRay-instrument the build of compiler-rt.
Reviewers: majnemer, rSerge, echristo
Subscribers: mehdi_amini, llvm-commits, mgorny
Differential Revision: https://reviews.llvm.org/D26597
llvm-svn: 287068
Dean Michael Berris