[arm64][cctest] Fix disassembly debug test on hardware.

The "test-disasm-arm64/DISASM_debug" test would fail on hardware because we
expected a "hlt" instruction instead of "brk". The former is specific to running
inside the simulator.

Bug: 
Change-Id: I7a5a3d4c1a93d03bbf4c934037c565d27379c2b5
Reviewed-on: https://chromium-review.googlesource.com/570442Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/master@{#46663}

test/cctest/test-disasm-arm64.cc

@@ -1869,13 +1869,19 @@ TEST_(debug) {
 
   // All debug codes should produce the same instruction, and the debug code
   // can be any uint32_t.
-  COMPARE(debug("message", 0, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 1, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 0xffff, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 0x10000, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 0x7fffffff, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 0x80000000u, BREAK), "hlt #0xdeb0");
-  COMPARE(debug("message", 0xffffffffu, BREAK), "hlt #0xdeb0");
+#ifdef USE_SIMULATOR
+  const char* expected_instruction = "hlt #0xdeb0";
+#else
+  const char* expected_instruction = "brk #0x0";
+#endif
+
+  COMPARE(debug("message", 0, BREAK), expected_instruction);
+  COMPARE(debug("message", 1, BREAK), expected_instruction);
+  COMPARE(debug("message", 0xffff, BREAK), expected_instruction);
+  COMPARE(debug("message", 0x10000, BREAK), expected_instruction);
+  COMPARE(debug("message", 0x7fffffff, BREAK), expected_instruction);
+  COMPARE(debug("message", 0x80000000u, BREAK), expected_instruction);
+  COMPARE(debug("message", 0xffffffffu, BREAK), expected_instruction);
 
   CLEANUP();
 }