[clang-tidy] Avoid repeated map lookups (NFC) (#132656)

Author: kazutakahirata

clang-tools-extra/clang-tidy/utils/HeaderGuard.cpp

@@ -88,11 +88,10 @@ class HeaderGuardPPCallbacks : public PPCallbacks {
         continue;
 
       // Look up Locations for this guard.
-      SourceLocation Ifndef =
-          Ifndefs[MacroEntry.first.getIdentifierInfo()].second;
+      const auto &Locs = Ifndefs[MacroEntry.first.getIdentifierInfo()];
+      SourceLocation Ifndef = Locs.second;
       SourceLocation Define = MacroEntry.first.getLocation();
-      SourceLocation EndIf =
-          EndIfs[Ifndefs[MacroEntry.first.getIdentifierInfo()].first];
+      SourceLocation EndIf = EndIfs[Locs.first];
 
       // If the macro Name is not equal to what we can compute, correct it in
       // the #ifndef and #define.