Fix heap-use-after-free coff::createPDB

[vitalybuka]

Summary

getInputSections returns std::vector by value and ArrayRef
pointed to destroyed temporarily.

[ruiu]

LGTM. Thanks! That may explain the flakiness of the buildbot.

lld/trunk/COFF/PDB.cpp

void coff::createPDB(StringRef Path, SymbolTable *Symtab,
   auto &TpiBuilder = Builder.getTpiBuilder();
   TpiBuilder.setVersionHeader(pdb::PdbTpiV80);
 
   // Add an empty IPI stream.
   auto &IpiBuilder = Builder.getIpiBuilder();
   IpiBuilder.setVersionHeader(pdb::PdbTpiV80);
 
   // Add Section Contributions.
-  ArrayRef<coff_section> InputSections = getInputSections(Symtab);
   std::vector<pdb::SectionContrib> Contribs =
-      pdb::DbiStreamBuilder::createSectionContribs(InputSections);
+      pdb::DbiStreamBuilder::createSectionContribs(getInputSections(Symtab));
   DbiBuilder.setSectionContribs(Contribs);
 
   // Add Section Map stream.
   ArrayRef<object::coff_section> Sections = {
       (const object::coff_section *)SectionTable.data(),
       SectionTable.size() / sizeof(object::coff_section)};
   std::vector<pdb::SecMapEntry> SectionMap =
       pdb::DbiStreamBuilder::createSectionMap(Sections);