Subzero: Use more "= default;" for ctors and dtors.

src/IceTargetLoweringARM32.h

Index: src/IceTargetLoweringARM32.h
diff --git a/src/IceTargetLoweringARM32.h b/src/IceTargetLoweringARM32.h
index b7efac3d1c04a5b5253577c89b1c3a8ce2756fbe..fdb025f883bea6185eb82844e9565b0356e5f5d7 100644
--- a/src/IceTargetLoweringARM32.h
+++ b/src/IceTargetLoweringARM32.h
@@ -341,7 +341,7 @@ protected:
   };
 
 private:
-  ~TargetARM32() override {}
+  ~TargetARM32() override = default;
 };
 
 class TargetDataARM32 final : public TargetDataLowering {
@@ -362,7 +362,7 @@ protected:
   explicit TargetDataARM32(GlobalContext *Ctx);
 
 private:
-  ~TargetDataARM32() override {}
+  ~TargetDataARM32() override = default;
   template <typename T> static void emitConstantPool(GlobalContext *Ctx);
 };