[vm] Evaluate abstract origin DIE offsets sooner in DWARF assembly output.

This greatly improves assembler performance in XCode 16, presumably by convincing the assembler it doesn't need to keep track of relocations for abstract origin labels.

TEST=ci
Bug: #43299
Bug: b/410018517
Change-Id: I68c6783d76bdf3c818c460c9a2cf559b88544993
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/422540
Commit-Queue: Ryan Macnak <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: rmacnak-google

runtime/vm/image_snapshot.cc

@@ -1076,15 +1076,11 @@ class DwarfAssemblyStream : public DwarfWriteStream {
   void InitializeAbstractOrigins(intptr_t size) {}
   void RegisterAbstractOrigin(intptr_t index) {
     // Label for DW_AT_abstract_origin references
-    stream_->Printf(".Lfunc%" Pd ":\n", index);
+    stream_->Printf("Lfunc%" Pd " = .-%s\n", index, kDebugInfoLabel);
   }
   void AbstractOrigin(intptr_t index) {
-    // Assignment to temp works around buggy Mac assembler.
-    stream_->Printf("Ltemp%" Pd " = .Lfunc%" Pd " - %s\n", temp_, index,
-                    kDebugInfoLabel);
-    stream_->Printf("%s Ltemp%" Pd "\n", kSizeDirectives[kInt32SizeLog2],
-                    temp_);
-    temp_++;
+    stream_->Printf("%s Lfunc%" Pd "\n", kSizeDirectives[kInt32SizeLog2],
+                    index);
   }
 
   // Methods for writing the assembly prologues for various DWARF sections.