[gimp-macos-build] Force python3.6 with libxml2

[Alex Samorukov <asamorukov src gnome org>]

commit abca2ccaa744af4104c99d3f960e59b60f8808e3
Author: Oleksii Samorukov <oleksii_samorukov mckinsey com>
Date:   Sun Oct 27 16:32:38 2019 +0100

    Force python3.6 with libxml2

 jhbuildrc-gtk-osx-gimp | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/jhbuildrc-gtk-osx-gimp b/jhbuildrc-gtk-osx-gimp
index a936c64..77525cc 100644
--- a/jhbuildrc-gtk-osx-gimp
+++ b/jhbuildrc-gtk-osx-gimp
@@ -157,6 +157,8 @@ environ_prepend('OBJCFLAGS', "-O3")
 # use our modulset
 moduleset = 'https://gitlab.gnome.org/samm-git/gtk-osx/raw/fork-test/modulesets-stable/gtk-osx.modules'
 
+module_extra_env['libxml2'] = { "PYTHON": os.path.expanduser("python3.6") }
+
 # And more...
 
 class _cmd_bootstrap_gtk_osx_gimp(jhbuild.commands.base.cmd_build):