Enable separate compilation.

Change-Id: I240665cd02706d11d2f8717b3e3276da435134cb
diff --git a/src/compiler_llvm/compilation_unit.h b/src/compiler_llvm/compilation_unit.h
index b206c80..9d87704 100644
--- a/src/compiler_llvm/compilation_unit.h
+++ b/src/compiler_llvm/compilation_unit.h
@@ -113,6 +113,8 @@
 
   size_t mem_usage_;
   uint16_t num_elf_funcs_;
+
+  static bool MaterializeFile(int input_fd, int output_fd, InstructionSet insn_set);
 };
 
 } // namespace compiler_llvm