Disable test MicroBenchmarks/XRay/FDRMode/fdrmode-bench.test on Darwin.

Test is failing because `__xray_log_select_mode("xray-fdr")` returns
XRAY_MODE_NOT_FOUND. Disable until it is fixed.

rdar://problem/44578416

Reviewers: dberris, devnexen

Reviewed By: dberris

Subscribers: mgorny, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D52278

llvm-svn: 342676

Author: vsapsai

MicroBenchmarks/XRay/CMakeLists.txt

@@ -1,2 +1,8 @@
 add_subdirectory(ReturnReference)
-add_subdirectory(FDRMode)
+if(NOT TARGET_OS STREQUAL "Darwin")
+  # FDRMode test is failing on Darwin because
+  # `__xray_log_select_mode("xray-fdr")` returns `XRAY_MODE_NOT_FOUND`.
+  #
+  # Disable the test until it is fixed. rdar://problem/44578416
+  add_subdirectory(FDRMode)
+endif()