Add command line support for enabling the optimizing compiler.

Also run tests with the optimizing compiler enabled when
the file art/USE_OPTIMIZING_COMPILER is present.

Change-Id: Ibc33eed62a43547bc3b9fe786d014c0d81b5add8
diff --git a/compiler/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index 03fc091..cb737ab 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -405,7 +405,7 @@
       // Is this the select pattern?
       // TODO: flesh out support for Mips.  NOTE: llvm's select op doesn't quite work here.
       // TUNING: expand to support IF_xx compare & branches
-      if (!cu_->compiler_backend->IsPortable() &&
+      if (!cu_->compiler->IsPortable() &&
           (cu_->instruction_set == kThumb2 || cu_->instruction_set == kX86) &&
           IsInstructionIfCcZ(mir->dalvikInsn.opcode)) {
         BasicBlock* ft = GetBasicBlock(bb->fall_through);