[DebugInfo] Use std::map::try_emplace (NFC)

This patch provides default member initialization for SymInfo, which
in turns allows us to call std::map::try_emplace without the value.

Author: kazutakahirata

llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

@@ -1902,8 +1902,8 @@ static Error createError(const Twine &Reason, llvm::Error E) {
 /// SymInfo contains information about symbol: it's address
 /// and section index which is -1LL for absolute symbols.
 struct SymInfo {
-  uint64_t Address;
-  uint64_t SectionIndex;
+  uint64_t Address = 0;
+  uint64_t SectionIndex = 0;
 };
 
 /// Returns the address of symbol relocation used against and a section index.
@@ -1921,7 +1921,7 @@ static Expected<SymInfo> getSymbolInfo(const object::ObjectFile &Obj,
   // in the object file
   if (Sym != Obj.symbol_end()) {
     bool New;
-    std::tie(CacheIt, New) = Cache.insert({*Sym, {0, 0}});
+    std::tie(CacheIt, New) = Cache.try_emplace(*Sym);
     if (!New)
       return CacheIt->second;