Propagate InstructionSetFeatures to ElfBuilder.

This is subset of CL171665 and it separates it into two.
It will be needed to generate .MIPS.abiflags ELF section.

Change-Id: I5557e7cb98d0fa1dc57c85cf6161e119c6d50a1a
diff --git a/compiler/image_test.cc b/compiler/image_test.cc
index 5763cec..3b622b5 100644
--- a/compiler/image_test.cc
+++ b/compiler/image_test.cc
@@ -99,6 +99,7 @@
       const std::vector<const DexFile*>& dex_files = class_linker->GetBootClassPath();
       std::unique_ptr<ElfWriter> elf_writer = CreateElfWriterQuick(
           compiler_driver_->GetInstructionSet(),
+          compiler_driver_->GetInstructionSetFeatures(),
           &compiler_driver_->GetCompilerOptions(),
           oat_file.GetFile());
       elf_writer->Start();