Generate CFI for stackless methods.

Generate at least a single no-op.
Otherwise it seems like CFI is missing.

Bug: 122379755
Test: ART_HEAP_POISONING=true ART_USE_READ_BARRIER=true ./art/test.py -r -t 137 --jit --32 --target
Change-Id: Id9206cb49ce976a03e1d50e6801abcefff537f60
diff --git a/compiler/optimizing/code_generator_arm_vixl.cc b/compiler/optimizing/code_generator_arm_vixl.cc
index 8204f1e..9c155f8 100644
--- a/compiler/optimizing/code_generator_arm_vixl.cc
+++ b/compiler/optimizing/code_generator_arm_vixl.cc
@@ -2093,6 +2093,8 @@
   }
 
   if (HasEmptyFrame()) {
+    // Ensure that the CFI opcode list is not empty.
+    GetAssembler()->cfi().Nop();
     return;
   }