Compiler changes for boot image extension.

Test: m test-art-host-gtest
Test: testrunnner.py --host --optimizing
Test: aosp_taimen-userdebug boots.
Test: run-gtest.sh
Test: testrunner.py --target --optimizing
Change-Id: I8e999c96ec908f26d8c529edc9d2a3be49a9379a
diff --git a/compiler/driver/compiler_options.h b/compiler/driver/compiler_options.h
index 98b15dc..e24da59 100644
--- a/compiler/driver/compiler_options.h
+++ b/compiler/driver/compiler_options.h
@@ -72,6 +72,7 @@
   enum class ImageType : uint8_t {
     kNone,                // JIT or AOT app compilation producing only an oat file but no image.
     kBootImage,           // Creating boot image.
+    kBootImageExtension,  // Creating boot image extension.
     kAppImage,            // Creating app image.
     kApexBootImage,       // Creating the apex image for jit/zygote experiment b/119800099.
   };
@@ -200,6 +201,11 @@
     return image_type_ == ImageType::kApexBootImage;
   }
 
+  // Are we compiling a boot image extension?
+  bool IsBootImageExtension() const {
+    return image_type_ == ImageType::kBootImageExtension;
+  }
+
   bool IsBaseline() const {
     return baseline_;
   }