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/image_test.h b/dex2oat/linker/image_test.h
index dc570da..d3d42b9 100644
--- a/dex2oat/linker/image_test.h
+++ b/dex2oat/linker/image_test.h
@@ -26,6 +26,7 @@
 #include "android-base/stringprintf.h"
 
 #include "art_method-inl.h"
+#include "base/file_utils.h"
 #include "base/unix_file/fd_file.h"
 #include "class_linker-inl.h"
 #include "common_compiler_test.h"