COFF: Remove an unused mutex declaration.

llvm-svn: 289415

lld/COFF/InputFiles.h

@@ -19,7 +19,6 @@
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/StringSaver.h"
 #include <memory>
-#include <mutex>
 #include <set>
 #include <vector>
 
@@ -202,7 +201,6 @@ private:
   std::vector<SymbolBody *> SymbolBodies;
   llvm::BumpPtrAllocator Alloc;
   std::unique_ptr<LTOModule> M;
-  static std::mutex Mu;
 };
 
 std::string toString(InputFile *File);