[Frontend] Name variable correctly.

Reported by: Kim Grasman!

llvm-svn: 250605
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index d4f2044..6e23411 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1986,8 +1986,8 @@
 }
 
 void ModuleSignature::add(StringRef Value) {
-  for (auto &S : Value)
-    add(S, 8);
+  for (auto &c : Value)
+    add(c, 8);
 }
 
 llvm::APInt ModuleSignature::getAsInteger() const {