Separate file utilities from utils.cc

Reduce the dependencies from utils.cc to arch/ subdirectories, etc.

Bug: 22322814
Test: make test-art-host
Change-Id: I4decd15ff4ec460735bfb58cebb1c6a1bf32b68f
diff --git a/dex2oat/linker/elf_writer_test.cc b/dex2oat/linker/elf_writer_test.cc
index 9f8ed77..8427e7b 100644
--- a/dex2oat/linker/elf_writer_test.cc
+++ b/dex2oat/linker/elf_writer_test.cc
@@ -16,6 +16,7 @@
 
 #include "elf_file.h"
 
+#include "base/file_utils.h"
 #include "base/unix_file/fd_file.h"
 #include "common_compiler_test.h"
 #include "elf_file.h"