Revert "Write dex files to oat file early."

This reverts commit 625a64aad13905d8a2454bf3cc0e874487b110d5.

Breaks the Mac build:

Undefined symbols for architecture i386:
  "_CloseArchive", referenced from:
      ... in oat_writer.o
ld: symbol(s) not found for architecture i386

Change-Id: I21608bc51437834e1e6abde9bcbe5e7d9998197e
diff --git a/runtime/oat.h b/runtime/oat.h
index 989e3f9..13fd6a4 100644
--- a/runtime/oat.h
+++ b/runtime/oat.h
@@ -31,7 +31,7 @@
 class PACKED(4) OatHeader {
  public:
   static constexpr uint8_t kOatMagic[] = { 'o', 'a', 't', '\n' };
-  static constexpr uint8_t kOatVersion[] = { '0', '7', '5', '\0' };
+  static constexpr uint8_t kOatVersion[] = { '0', '7', '4', '\0' };
 
   static constexpr const char* kImageLocationKey = "image-location";
   static constexpr const char* kDex2OatCmdLineKey = "dex2oat-cmdline";