ART: Use optimizing compiler in image_test

Expose some compiler options so we can run the image test with
the optimizing compiler without running into a stack overflow.

Also allow a variable amount of threads in CreateCompilerDriver.
Use 16 as a middle ground on the host to speed up the otherwise
now slowed-down test.

Bug: 27240085
Bug: 27552475
Change-Id: I8db5055d32ae722c8f430903244faa9166cc4886
diff --git a/compiler/driver/compiler_options.h b/compiler/driver/compiler_options.h
index a220959..4db82a6 100644
--- a/compiler/driver/compiler_options.h
+++ b/compiler/driver/compiler_options.h
@@ -159,10 +159,16 @@
   size_t GetInlineDepthLimit() const {
     return inline_depth_limit_;
   }
+  void SetInlineDepthLimit(size_t limit) {
+    inline_depth_limit_ = limit;
+  }
 
   size_t GetInlineMaxCodeUnits() const {
     return inline_max_code_units_;
   }
+  void SetInlineMaxCodeUnits(size_t units) {
+    inline_max_code_units_ = units;
+  }
 
   double GetTopKProfileThreshold() const {
     return top_k_profile_threshold_;