[lld/mac] Fix start-stop.s test with expensive checks enabled

[thakis]

Summary

See e.g. https://lab.llvm.org/buildbot/#/builders/16/builds/14317
Not 100% sure why this fails yet, but this fixes it. Let's get
the bots green again first :)

[int3]

lgtm

lld/MachO/OutputSegment.cpp

 
 void OutputSegment::sortOutputSections() {
   // Must be stable_sort() to keep special sections such as
   // S_THREAD_LOCAL_REGULAR in input order.
   llvm::stable_sort(sections, compareByOrder<OutputSection *>(sectionOrder));
 }
 
 void macho::sortOutputSegments() {
-  // sort() instead of stable_sort() is fine because segmentOrder() is
-  // name-based and getOrCreateOutputSegment() makes there's only a single
-  // segment for every name.
-  llvm::sort(outputSegments, compareByOrder<OutputSegment *>(segmentOrder));
+  llvm::stable_sort(outputSegments,
+                    compareByOrder<OutputSegment *>(segmentOrder));
 }
 
 static DenseMap<StringRef, OutputSegment *> nameToOutputSegment;
 std::vector<OutputSegment *> macho::outputSegments;
 
 OutputSegment *macho::getOrCreateOutputSegment(StringRef name) {
   OutputSegment *&segRef = nameToOutputSegment[name];
   if (segRef)