Use binary_safe_diff from arcanist

Summary:
binary_safe_diff is needed in arcanist too. Moved it over to
arcanist. See D2915.

Test Plan: diffusion page rendered correctly on binary file.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D2916

Author: Jason Ge

scripts/repository/binary_safe_diff.sh

@@ -23,11 +23,11 @@ protected function executeQuery() {
     $repository = $drequest->getRepository();
 
     $commit = $drequest->getCommit();
-    $root = phutil_get_library_root('phabricator');
+    $arc_root = phutil_get_library_root('arcanist');
 
     $future = $repository->getRemoteCommandFuture(
       'diff --diff-cmd %s -x -U%d -c %d %s%s@',
-      $root.'/../scripts/repository/binary_safe_diff.sh',
+      $arc_root.'/../scripts/repository/binary_safe_diff.sh',
       $this->getLinesOfContext(),
       $commit,
       $repository->getRemoteURI(),