Add ELF index to art::compiler_llvm::CompilationUnit.

We need an ELF index to remember which ELF image contains
the CompiledMethod or CompiledInvokeStub.

(cherry picked from commit df612fb98fabeec2fa7277c7ab332589fa38283c)

Change-Id: Ic8a4aca7d030685e156c9f3fe632bf45a5c4d02b
diff --git a/src/compiler_llvm/compiler_llvm.cc b/src/compiler_llvm/compiler_llvm.cc
index 7563fe0..d528615 100644
--- a/src/compiler_llvm/compiler_llvm.cc
+++ b/src/compiler_llvm/compiler_llvm.cc
@@ -119,7 +119,7 @@
   // Allocate compilation unit
   size_t cunit_idx = cunits_.size();
 
-  curr_cunit_ = new CompilationUnit(insn_set_);
+  curr_cunit_ = new CompilationUnit(insn_set_, cunit_idx);
 
   // Setup output filename
   curr_cunit_->SetElfFileName(