Use ATTRIBUTE_UNUSED more.

Use it in lieu of UNUSED(), which had some incorrect uses.

Change-Id: If247dce58b72056f6eea84968e7196f0b5bef4da
diff --git a/compiler/dex/quick/quick_compiler.cc b/compiler/dex/quick/quick_compiler.cc
index c2fe553..6673ea8 100644
--- a/compiler/dex/quick/quick_compiler.cc
+++ b/compiler/dex/quick/quick_compiler.cc
@@ -851,8 +851,8 @@
       InstructionSetPointerSize(GetCompilerDriver()->GetInstructionSet())));
 }
 
-Mir2Lir* QuickCompiler::GetCodeGenerator(CompilationUnit* cu, void* compilation_unit) {
-  UNUSED(compilation_unit);
+Mir2Lir* QuickCompiler::GetCodeGenerator(CompilationUnit* cu,
+                                         void* compilation_unit ATTRIBUTE_UNUSED) {
   Mir2Lir* mir_to_lir = nullptr;
   switch (cu->instruction_set) {
 #ifdef ART_ENABLE_CODEGEN_arm