[BOLT][NFC] Check errors from Obj.dynamicEntries

[Amir]

Summary

Addresses fuzzer crash

[rafauler]

LGTM

bolt/lib/Rewrite/RewriteInstance.cpp

if (!DynamicPhdr) {
     return Error::success();
   }
 
   if (DynamicPhdr->p_memsz != DynamicPhdr->p_filesz)
     return createStringError(errc::executable_format_error,
                              "dynamic section sizes should match");
 
   // Go through all dynamic entries to locate entries of interest.
-  typename ELFT::DynRange DynamicEntries =
-      cantFail(Obj.dynamicEntries(), "error accessing dynamic table");
+  auto DynamicEntriesOrErr = Obj.dynamicEntries();
+  if (!DynamicEntriesOrErr)
+    return DynamicEntriesOrErr.takeError();
+  typename ELFT::DynRange DynamicEntries = DynamicEntriesOrErr.get();
 
   for (const Elf_Dyn &Dyn : DynamicEntries) {
     switch (Dyn.d_tag) {
     case ELF::DT_INIT:
       if (!BC->HasInterpHeader) {
         LLVM_DEBUG(dbgs() << "BOLT-DEBUG: Set start function address\n");
         BC->StartFunctionAddress = Dyn.getPtr();
       }