[llvm] Reduce llvm-gsymutil memory usage (PR #91023)

[via llvm-commits]

================
@@ -612,11 +617,16 @@ Error DwarfTransformer::convert(uint32_t NumThreads, OutputAggregator &Out) {
       DWARFDie Die = getDie(*CU);
       if (Die) {
         CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
-        pool.async([this, CUI, &LogMutex, &Out, Die]() mutable {
+        pool.async([this, CUI, &CU, &LogMutex, &Out, Die]() mutable {
           std::string storage;
           raw_string_ostream StrStream(storage);
           OutputAggregator ThreadOut(Out.GetOS() ? &StrStream : nullptr);
           handleDie(ThreadOut, CUI, Die);
+          // Release the line table once we're done.
+          DICtx.clearLineTableForUnit(CU.get());
+          // Free any DIEs that were allocated by the DWARF parser.
+          // If/when they're needed by other CU's, they'll be recreated.
+          CU->clearDIEs(false);
----------------
jeffreytan81 wrote:

Nit: `/*KeepCUDie=*/false`

https://github.com/llvm/llvm-project/pull/91023