Remove some unused variables to clean up the -Werror build

llvm-svn: 252580
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 437e671..21b9126 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -749,8 +749,8 @@
 
   assert(InProlog && "ChkStkStub called outside prolog!");
 
-  MachineInstrBuilder CI = BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
-                               .addExternalSymbol("__chkstk_stub");
+  BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
+      .addExternalSymbol("__chkstk_stub");
 
   return MBBI;
 }