Fix system_test (#5528)

Git since v2.11 no longer defaults to 7-hexdigits for short object
abbreviation.

See git/git@e6c587c

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: povilas

lib/elixir/test/elixir/system_test.exs

@@ -13,7 +13,7 @@ defmodule SystemTest do
     assert is_binary build_info[:version]
 
     if build_info[:revision] != "" do
-      assert String.length(build_info[:revision]) == 7
+      assert String.length(build_info[:revision]) >= 7
     end
 
     version_file = Path.join([__DIR__, "../../../..", "VERSION"]) |> Path.expand