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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198737 91177308-0d34-0410-b5e6-96231b3b80d8

lib/ExecutionEngine/RuntimeDyld/ObjectImageCommon.h

@@ -20,6 +20,10 @@
 
 namespace llvm {
 
+namespace object {
+  class ObjectFile;
+}
+
 class ObjectImageCommon : public ObjectImage {
   ObjectImageCommon(); // = delete
   ObjectImageCommon(const ObjectImageCommon &other); // = delete
@@ -42,6 +46,8 @@ public:
   {
     ObjFile = object::ObjectFile::createObjectFile(Buffer->getMemBuffer());
   }
+  ObjectImageCommon(object::ObjectFile* Input)
+  : ObjectImage(NULL), ObjFile(Input)  {}
   virtual ~ObjectImageCommon() { delete ObjFile; }
 
   virtual object::symbol_iterator begin_symbols() const