Subzero: Add -Wshadow to the build.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index a5b52ce91ca8413b493a8eee62a94fb4fe8fa7c9..6161b8132dc7f5b32c219da7e0c70c7e16e3d266 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -402,7 +402,7 @@ protected:
   /// Perhaps there is some difference when the location is unaligned.
   static const char *getEmit32Directive() { return ".long"; }
 
-  explicit TargetDataLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
+  explicit TargetDataLowering(GlobalContext *MyCtx) : Ctx(MyCtx) {}
   GlobalContext *Ctx;
 };
 
@@ -422,7 +422,7 @@ public:
   virtual void lower() {}
 
 protected:
-  explicit TargetHeaderLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
+  explicit TargetHeaderLowering(GlobalContext *MyCtx) : Ctx(MyCtx) {}
   GlobalContext *Ctx;
 };