Check that the String class is not movable in String.equals intrinsics.

Test: art/test.py
Bug: 68181300
Bug: 67628039
Change-Id: I66afa3ea010f758125f8aec79509f0255cb5ea03
diff --git a/compiler/optimizing/intrinsics.h b/compiler/optimizing/intrinsics.h
index 2d93f23..7594d4a 100644
--- a/compiler/optimizing/intrinsics.h
+++ b/compiler/optimizing/intrinsics.h
@@ -165,6 +165,8 @@
  protected:
   IntrinsicVisitor() {}
 
+  static void AssertNonMovableStringClass();
+
  private:
   DISALLOW_COPY_AND_ASSIGN(IntrinsicVisitor);
 };