[lld] [lld-macho] Support archives without index (PR #132942)

[Leonard Grey via llvm-commits]

================
@@ -2156,9 +2156,34 @@ ArchiveFile::ArchiveFile(std::unique_ptr<object::Archive> &&f, bool forceHidden)
 void ArchiveFile::addLazySymbols() {
   // Avoid calling getMemoryBufferRef() on zero-symbol archive
   // since that crashes.
-  if (file->isEmpty() || file->getNumberOfSymbols() == 0)
+  if (file->isEmpty())
     return;
 
+  if (file->getNumberOfSymbols() == 0) {
+    // No index, treat each child as a lazy object file.
+    Error e = Error::success();
+    for (const object::Archive::Child &c : file->children(e)) {
+      // Check `seen` but don't insert so a future eager load can still happen.
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speednoisemovement wrote:

I was going off the logic in Driver.cpp, specifically:
```
      // Command-line loads take precedence. If file is previously loaded via
      // command line, or is loaded via LC_LINKER_OPTION and being loaded via
      // LC_LINKER_OPTION again, using the cached archive is enough.
```
so I guess it's your scenario but s/force_load/LC_LINKER_OPTION. I think we would actually drop the force load in that case. Is that a bug?

https://github.com/llvm/llvm-project/pull/132942