Add missing 'override', fixing compilation with some compilers since SVN r337950

llvm-svn: 337952
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.h b/llvm/lib/Target/ARM/ARMAsmPrinter.h
index 50f3ede..0ba4bc0 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.h
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.h
@@ -102,7 +102,7 @@
   void EmitXXStructor(const DataLayout &DL, const Constant *CV) override;
   void EmitGlobalVariable(const GlobalVariable *GV) override;
 
-  MCSymbol *GetCPISymbol(unsigned CPID) const;
+  MCSymbol *GetCPISymbol(unsigned CPID) const override;
 
   // lowerOperand - Convert a MachineOperand into the equivalent MCOperand.
   bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp);