Make out arguments non-reference types.

Also, tidy some portable related code.

Change-Id: I67c8aa52eef8b556ca117ecda1b1e75465ba06a5
diff --git a/compiler/llvm/llvm_compilation_unit.cc b/compiler/llvm/llvm_compilation_unit.cc
index d23706d..1d027f9 100644
--- a/compiler/llvm/llvm_compilation_unit.cc
+++ b/compiler/llvm/llvm_compilation_unit.cc
@@ -199,7 +199,8 @@
   std::string target_triple;
   std::string target_cpu;
   std::string target_attr;
-  CompilerDriver::InstructionSetToLLVMTarget(GetInstructionSet(), target_triple, target_cpu, target_attr);
+  CompilerDriver::InstructionSetToLLVMTarget(GetInstructionSet(), &target_triple, &target_cpu,
+                                             &target_attr);
 
   std::string errmsg;
   const ::llvm::Target* target =