[lld-macho] Fix '-merge-objc-categories' win64 build

Author: Alex B

lld/MachO/InputSection.h

@@ -192,8 +192,10 @@ struct StringPiece {
   // Only set if deduplicating literals
   uint32_t hash : 31;
   // Offset from the start of the containing output section.
-  uint64_t outSecOff : 56;
-  LinkerOptReason linkerOptimizeReason : 8;
+  uint64_t outSecOff : 48;
+  // Have to declare the 'linkerOptimizeReason' and 'live' as uint64_t so that
+  // the MSVC compiler will merge the storage of it and 'outSecOff' above.
+  uint64_t /*LinkerOptReason*/ linkerOptimizeReason : 8;
 
   bool shouldOmitFromOutput() const {
     return !live || linkerOptimizeReason != LinkerOptReason::NotOptimized;

lld/MachO/ObjC.cpp

@@ -786,7 +786,7 @@ bool ObjcCategoryMerger::parseCatInfoToExtInfo(InfoInputCategory &catInfo,
 
   if (extInfo.baseClassName.empty()) {
     llvm::StringRef classPrefix("_OBJC_CLASS_$_");
-    if (!classSym->getName().startswith(classPrefix))
+    if (!classSym->getName().starts_with(classPrefix))
       return registerError(
           "Base class symbol does not start with '_OBJC_CLASS_$_'");
 
@@ -1137,7 +1137,7 @@ bool ObjcCategoryMerger::collectAndValidateCategoriesData() {
 
     for (const Reloc &r : catListCisec->relocs) {
       auto *sym = cast<Defined>(r.referent.get<Symbol *>());
-      if (!sym || !sym->getName().startswith("__OBJC_$_CATEGORY_"))
+      if (!sym || !sym->getName().starts_with("__OBJC_$_CATEGORY_"))
         continue; // Only support ObjC categories (no swift + @objc)
 
       auto *catBodyIsec =