[gimp-macos-build] README: minor update.

[Jehan <jehanp src gnome org>]

commit 23be532edf7dd6a4e116133a933120da91109028
Author: Jehan <jehan girinstud io>
Date:   Thu Dec 3 22:00:45 2020 +0100

    README: minor update.
    
    The real goal of this commit is to trigger a push because we asked for
    the Github mirror to be reinstated (see Infrastructure#495).

 README.md | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/README.md b/README.md
index da71b33..702db05 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,10 @@ of the [gtk-osx](https://gitlab.gnome.org/GNOME/gtk-osx) project (`gimp` branch)
 Fork adds modules related to GIMP and some gimp-specific patches to GTK.
 Currently build is done using CircleCI.
 
-Because CircleCI is not supporting gitlab [yet] there is a [GitHub 
mirror](https://github.com/GNOME/gimp-macos-build) of this repository.
+Because CircleCI is not supporting gitlab [yet] there is a [GitHub
+mirror](https://github.com/GNOME/gimp-macos-build) of this repository.
+To get access to the Circle-CI build administration, packagers need to
+ask admin access to this Github repository.
 
 ## Before you starting