Opt compiler: Add disassembly to the '.cfg' output.

This is automatically added to the '.cfg' output when using the usual
`--dump-cfg` option.

Change-Id: I864bfc3a8299c042e72e451cc7730ad8271e4deb
diff --git a/compiler/utils/assembler.h b/compiler/utils/assembler.h
index 0381af3..ee2d594 100644
--- a/compiler/utils/assembler.h
+++ b/compiler/utils/assembler.h
@@ -386,6 +386,7 @@
 
   // Size of generated code
   virtual size_t CodeSize() const { return buffer_.Size(); }
+  virtual const uint8_t* CodeBufferBaseAddress() const { return buffer_.contents(); }
 
   // Copy instructions out of assembly buffer into the given region of memory
   virtual void FinalizeInstructions(const MemoryRegion& region) {