Roll mac_toolchain to 2b69be620

Relevant commit:
  2b69be620 mac_toolchain: update file permissions post-install
  894cac284 mac_toolchain: add "package" command
  09ed0cfc0 mac_toolchain: include symlinks

BUG=475693
TBR=iannucci@chromium.org

Change-Id: I65d146fd99ab8dd378b04714b8e3b88e0cf51907
Reviewed-on: https://chromium-review.googlesource.com/775667
Commit-Queue: Sergey Berezin <sergeyberezin@chromium.org>
Reviewed-by: Sergey Berezin <sergeyberezin@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>

cipd_manifest.txt

@@ -14,4 +14,4 @@ infra/tools/luci/vpython/${platform}  git_revision:a3d636052088db3daa48413b3e209
 infra/tools/luci/led/${platform}  git_revision:9010ba713ba6fc9982c412161150a5cd70d5b623
 
 # Mac toolchain installer
-infra/tools/mac_toolchain/${os=mac}-${arch} git_revision:38eded8baee0633bffd47c1f3028006e7c84661e
+infra/tools/mac_toolchain/${os=mac}-${arch} git_revision:2b69be6203f56a970202d9b5984557c0453b4eb0