[debuginfo-tests] Skip optnone-loops.cpp on Darwin

This is failing on GreenDragon:
http://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/24745/

GitOrigin-RevId: 2993850237b089d134cec2776312b61ef9bff757
diff --git a/dexter-tests/optnone-loops.cpp b/dexter-tests/optnone-loops.cpp
index 283c766..c7fe7eb 100644
--- a/dexter-tests/optnone-loops.cpp
+++ b/dexter-tests/optnone-loops.cpp
@@ -3,6 +3,7 @@
 
 // REQUIRES: lldb
 // UNSUPPORTED: system-windows
+// UNSUPPORTED: system-darwin
 
 // RUN: %dexter --fail-lt 1.0 -w \
 // RUN:     --builder 'clang' --debugger 'lldb' \