Revised CL for customisable logging (replacing printfs).

runtime/bin/file_macos.cc

Index: runtime/bin/file_macos.cc
===================================================================
--- runtime/bin/file_macos.cc	(revision 14903)
+++ runtime/bin/file_macos.cc	(working copy)
@@ -12,6 +12,7 @@
 #include <limits.h>
 
 #include "bin/builtin.h"
+#include "bin/log.h"
 
 class FileHandle {
  public:
@@ -43,7 +44,7 @@
     const int kBufferSize = 1024;
     char error_message[kBufferSize];
     strerror_r(errno, error_message, kBufferSize);
-    fprintf(stderr, "%s\n", error_message);
+    Log::PrintErr("%s\n", error_message);
   }
   handle_->set_fd(kClosedFd);
 }