Mark override to a function which overrides a virtual one

[anhtuyen]

Summary

Function void run() on line 286 overrides a virtual function on line 92.
Not marking it override will cause a build failure when we use -Werror (every warning is treated as an error).

[kbobyrev]

Thanks!

clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp

class Export : public Command {
   llvm::cl::opt<std::string> OutputFile{
       "output-file",
       llvm::cl::Positional,
       llvm::cl::Required,
       llvm::cl::desc("Output file for export"),
   };
 
 public:
-  void run() {
+  void run() override {
     using namespace clang::clangd;
     // Read input file (as specified in global option)
     auto Buffer = llvm::MemoryBuffer::getFile(IndexLocation);
     if (!Buffer) {
       llvm::errs() << llvm::formatv("Can't open {0}", IndexLocation) << "\n";
       return;
     }