Re-apply r196639: Add support for archives and object file caching under MCJIT.

I believe the bot failures on linux systems were due to overestimating the
alignment of object-files within archives, which are only guaranteed to be
two-byte aligned. I have reduced the alignment in
RuntimeDyldELF::createObjectImageFromFile accordingly.

llvm-svn: 198737
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
index 3adf827..181964f 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
@@ -140,7 +140,9 @@
                                     const SymbolTableMap &Symbols,
                                     StubMap &Stubs);
   virtual bool isCompatibleFormat(const ObjectBuffer *Buffer) const;
+  virtual bool isCompatibleFile(const object::ObjectFile *Buffer) const;
   virtual ObjectImage *createObjectImage(ObjectBuffer *InputBuffer);
+  virtual ObjectImage *createObjectImageFromFile(object::ObjectFile *Obj);
   virtual void registerEHFrames();
   virtual void deregisterEHFrames();
   virtual void finalizeLoad(ObjSectionToIDMap &SectionMap);