Move .oat files to ELF format

Generates .oat in ELF file format using MCLinker
- Uses MCLinker IRBuilder to create a synthetic .o from OatWriter output.
- Uses new ElfFile for prelinking to support art image optimizations.

Adapted OatFile to load using dlopen, ElfFile, or memory, removing raw MemMap mechanism.

Changed image code to not assume oat data will be immediately after
image to allow space for ELF headers.

Passes test-art and works with installd.

Change-Id: Idc026eddb5de93f4b97490c405f3ed7b39589749
diff --git a/src/compiler_llvm/compilation_unit.cc b/src/compiler_llvm/compilation_unit.cc
index 78bc50d..bd2d8fc 100644
--- a/src/compiler_llvm/compilation_unit.cc
+++ b/src/compiler_llvm/compilation_unit.cc
@@ -178,39 +178,10 @@
 
 bool CompilationUnit::MaterializeToRawOStream(llvm::raw_ostream& out_stream) {
   // Lookup the LLVM target
-  const char* target_triple = NULL;
-  const char* target_cpu = "";
-  const char* target_attr = NULL;
-
-  InstructionSet insn_set = GetInstructionSet();
-  switch (insn_set) {
-  case kThumb2:
-    target_triple = "thumb-none-linux-gnueabi";
-    target_cpu = "cortex-a9";
-    target_attr = "+thumb2,+neon,+neonfp,+vfp3,+db";
-    break;
-
-  case kArm:
-    target_triple = "armv7-none-linux-gnueabi";
-    // TODO: Fix for Nexus S.
-    target_cpu = "cortex-a9";
-    // TODO: Fix for Xoom.
-    target_attr = "+v7,+neon,+neonfp,+vfp3,+db";
-    break;
-
-  case kX86:
-    target_triple = "i386-pc-linux-gnu";
-    target_attr = "";
-    break;
-
-  case kMips:
-    target_triple = "mipsel-unknown-linux";
-    target_attr = "mips32r2";
-    break;
-
-  default:
-    LOG(FATAL) << "Unknown instruction set: " << insn_set;
-  }
+  std::string target_triple;
+  std::string target_cpu;
+  std::string target_attr;
+  Compiler::InstructionSetToLLVMTarget(GetInstructionSet(), target_triple, target_cpu, target_attr);
 
   std::string errmsg;
   const llvm::Target* target =
@@ -324,7 +295,6 @@
   return true;
 }
 
-
 bool CompilationUnit::ExtractCodeAndPrelink(const std::string& elf_image) {
   if (GetInstructionSet() == kX86) {
     compiled_code_.push_back(0xccU);