Use internal storage for command line option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139079 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86VZeroUpper.cpp b/lib/Target/X86/X86VZeroUpper.cpp
index d87efc9..3958494 100644
--- a/lib/Target/X86/X86VZeroUpper.cpp
+++ b/lib/Target/X86/X86VZeroUpper.cpp
@@ -62,7 +62,7 @@
   return Changed;
 }
 
-bool isCallToModuleFn(const MachineInstr *MI) {
+static bool isCallToModuleFn(const MachineInstr *MI) {
   assert(MI->getDesc().isCall() && "Isn't a call instruction");
 
   for (int i = 0, e = MI->getNumOperands(); i != e; ++i) {