Function can't be static in debug build

Author: localspook

clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp

@@ -51,7 +51,7 @@ class ExpandModularHeadersPPCallbacks::FileRecorder {
 
   /// Makes sure we have contents for all the files we were interested in.
   /// Ideally `FilesToRecord` should be empty.
-  static void checkAllFilesRecorded() {
+  void checkAllFilesRecorded() {
     LLVM_DEBUG({
       for (auto FileEntry : FilesToRecord)
         llvm::dbgs() << "Did not record contents for input file: "