Tidy logging code not using UNIMPLEMENTED.

Change-Id: I7a79c1671a6ff8b2040887133b3e0925ef9a3cfe
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index 359d6af..7e19e15 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -111,7 +111,7 @@
 #else
   // Only warn if not Intel as Intel doesn't have cache flush instructions.
 #if !defined(__i386__) && !defined(__x86_64__)
-  LOG(WARNING) << "UNIMPLEMENTED: cache flush";
+  UNIMPLEMENTED(WARNING) << "cache flush";
 #endif
 #endif
 }