[CodeGen] Add missing header guard to LibcallLoweringInfo.h

Introduced by #164987

Author: tomershafir

llvm/include/llvm/CodeGen/LibcallLoweringInfo.h

@@ -6,6 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifndef LLVM_CODEGEN_LIBCALLLOWERINGINFO_H
+#define LLVM_CODEGEN_LIBCALLLOWERINGINFO_H
+
 #include "llvm/IR/RuntimeLibcalls.h"
 
 namespace llvm {
@@ -64,3 +67,5 @@ class LibcallLoweringInfo {
 };
 
 } // end namespace llvm
+
+#endif // LLVM_CODEGEN_LIBCALLLOWERINGINFO_H