MicroBenchmarks/XRay tests FAIL to link

[rorth]

While building LLVM 17.0.0 rc1 on Solaris/amd64, two test-suite tests FAILed to link, breaking the test-suite build:

FAILED: MicroBenchmarks/XRay/ReturnReference/retref-bench
[...]
Undefined                       first referenced
 symbol                             in file
__xray_set_handler                  MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o
__xray_patch                        MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o
__xray_remove_handler               MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o
__xray_unpatch                      MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o
ld: fatal: symbol referencing errors

FAILED: MicroBenchmarks/XRay/FDRMode/fdrmode-bench 
[...]
Undefined                       first referenced
 symbol                             in file
__xray_log_flushLog                 MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_log_init_mode                MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_patch                        MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_remove_customevent_handler   MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_unpatch                      MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_log_finalize                 MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
__xray_log_select_mode              MicroBenchmarks/XRay/FDRMode/CMakeFiles/fdrmode-bench.dir/fdrmode-bench.cc.o
ld: fatal: symbol referencing errors

This is a regression from LLVM 16 and caused by problems of the MicroBenchmarks/XRay/CMakeLists.txt XRay checks. The build log shows

-- Performing Test COMPILER_HAS_FXRAY_INSTRUMENT
-- Performing Test COMPILER_HAS_FXRAY_INSTRUMENT - Success
-- Looking for include file xray/xray_interface.h
-- Looking for include file xray/xray_interface.h - found
-- XRay tests enabled

• The first test obviously passed for a test-release.sh build: the just-built clang always supports the -fxray-instrument flag.
• The test for xray/xray_interface.h always passes as well: the XRay headers are always installed, irrespective whether XRay is supported on a particular target. I believe this is something that should be fixed, thus avoiding the problem in the first place.
• The cmake tests are thus at least incomplete, wrong in the worst case. They should check if an executable using XRay can be compiled and linked. This way, the hack in CMakeLists.txt to check for x86 && !darwin (which is practically guaranteed to become stale) can be avoided.

[rorth]

Still happens in LLVM 18.1.0 rc2 on Solaris/amd64.