[ORC-RT] Fix objc selector corruption

[benlangmuir]

Summary

We were writing a pointer to a selector string into the contents of astring instead of overwriting the pointer to the string, leading tocorruption. This was causing non-deterministic failures of the 'trivial-objc-methods' test case.

[lhames]

LGTM. Thanks Ben!

compiler-rt/lib/orc/macho_platform.cpp

Error registerObjCSelectors(
   if (ORC_RT_UNLIKELY(!sel_registerName))
     return make_error<StringError>("sel_registerName is not available");
 
   for (const auto &ObjCSelRefs : ObjCSelRefsSections) {
 
     if (auto Err = validatePointerSectionExtent("__objc_selrefs", ObjCSelRefs))
       return Err;
 
-    for (uintptr_t SelEntry : ObjCSelRefs.toSpan<uintptr_t>()) {
+    for (uintptr_t &SelEntry : ObjCSelRefs.toSpan<uintptr_t>()) {
       const char *SelName = reinterpret_cast<const char *>(SelEntry);
       auto Sel = sel_registerName(SelName);
-      *reinterpret_cast<SEL *>(SelEntry) = Sel;
+      *reinterpret_cast<SEL *>(&SelEntry) = Sel;
     }
   }
 
   return Error::success();
 }
 
 Error registerObjCClasses(
     const std::vector<ExecutorAddrRange> &ObjCClassListSections,