Fix gcc build error after D105519

[TaoPan]

Summary

Same as 3bec7ed59e1b

[TaoPan]

@jpienaar Could you please have a review?

[sbc100]

thanks!

lld/wasm/SyntheticSections.h

return lhs.state == rhs.state && lhs.importModule == rhs.importModule &&
          lhs.importName == rhs.importName && lhs.type == rhs.type;
 }
 
 } // namespace wasm
 } // namespace lld
 
 // `ImportKey<T>` can be used as a key in a `DenseMap` if `T` can be used as a
 // key in a `DenseMap`.
-template <typename T> struct llvm::DenseMapInfo<lld::wasm::ImportKey<T>> {
+namespace llvm {
+template <typename T> struct DenseMapInfo<lld::wasm::ImportKey<T>> {
   static lld::wasm::ImportKey<T> getEmptyKey() {
     typename lld::wasm::ImportKey<T> key(llvm::DenseMapInfo<T>::getEmptyKey());
     key.state = lld::wasm::ImportKey<T>::State::Empty;
     return key;
   }
   static lld::wasm::ImportKey<T> getTombstoneKey() {
     typename lld::wasm::ImportKey<T> key(llvm::DenseMapInfo<T>::getEmptyKey());
     key.state = lld::wasm::ImportKey<T>::State::Tombstone;
     return key;
   }
   static unsigned getHashValue(const lld::wasm::ImportKey<T> &key) {
     uintptr_t hash = hash_value(key.importModule);
     hash = hash_combine(hash, key.importName);
     hash = hash_combine(hash, llvm::DenseMapInfo<T>::getHashValue(key.type));
     hash = hash_combine(hash, key.state);
     return hash;
   }
   static bool isEqual(const lld::wasm::ImportKey<T> &lhs,
                       const lld::wasm::ImportKey<T> &rhs) {
     return lhs == rhs;
   }
 };
+} // end namespace llvm
 
 namespace lld {
 namespace wasm {
 
 class ImportSection : public SyntheticSection {
 public:
   ImportSection() : SyntheticSection(llvm::wasm::WASM_SEC_IMPORT) {}
   bool isNeeded() const override { return getNumImports() > 0; }