[gimp-macos-build] jhbuildrc-gtk-osx-gimp: gimp-help is now ported to Python 3.

[Jehan <jehanp src gnome org>]

commit 4fc596735ae417e6f5f7c2e2ad1e8cd2c3888998
Author: Jehan <jehan girinstud io>
Date:   Fri Jul 23 19:47:35 2021 +0200

    jhbuildrc-gtk-osx-gimp: gimp-help is now ported to Python 3.
    
    Apparently PYTHON env variable is currently set to 'python' (and it
    turns out to be Python 2.7.10 on Circle-CI), not sure where this
    variable is set, but let's override it ourselves.

 jhbuildrc-gtk-osx-gimp | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/jhbuildrc-gtk-osx-gimp b/jhbuildrc-gtk-osx-gimp
index 21d1fe2..8df47f6 100644
--- a/jhbuildrc-gtk-osx-gimp
+++ b/jhbuildrc-gtk-osx-gimp
@@ -160,6 +160,9 @@ moduleset = 'https://gitlab.gnome.org/samm-git/gtk-osx/raw/gimp/modulesets-stabl
 # force python 3.6 for the libxml2 to avoid build issues
 module_extra_env['libxml2'] = { "ac_cv_path_PYTHON": "python3.6" }
 
+# force python 3.6 for gimp-help.
+module_extra_env['gimp-help-git'] = { "PYTHON": "python3.6" }
+
 # meson needs UTF-8 charset for build python scripts to work correctly
 module_extra_env['meson'] = { "LC_ALL": "en_US.UTF-8" }