[gobject-introspection/gnome-3-32] ci: work around mingw python detection issue

[Christoph Reiter <creiter src gnome org>]

commit 8e283ff6eff9b5fd2a7cda259ba4628d7c24eaf4
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Fri May 3 21:53:43 2019 +0200

    ci: work around mingw python detection issue
    
    Some recent MSYS2 update made autotools no longer detect python3.
    I don't have to time to debug atm, so force the interpreter with
    the PYTHON env var for now.

 .gitlab-ci/test-msys2-autotools.sh | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci/test-msys2-autotools.sh b/.gitlab-ci/test-msys2-autotools.sh
index 1029864b..48d3db98 100644
--- a/.gitlab-ci/test-msys2-autotools.sh
+++ b/.gitlab-ci/test-msys2-autotools.sh
@@ -21,6 +21,7 @@ pacman --noconfirm -S --needed \
     mingw-w64-$MSYS2_ARCH-glib2 \
     mingw-w64-$MSYS2_ARCH-gtk-doc
 
+export PYTHON="$(which python3)"
 ./autogen.sh
 
 make -j6