[gdk-pixbuf/win-ci-xsltproc-fix] ci: install mingw xsltproc

[Christoph Reiter <creiter src gnome org>]

commit 402b92263916ca76335772c4c40b04824df9f012
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Fri Feb 1 11:02:22 2019 +0100

    ci: install mingw xsltproc

 .gitlab/ci/test-msys2.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab/ci/test-msys2.sh b/.gitlab/ci/test-msys2.sh
index 008b7c437..1331852dd 100644
--- a/.gitlab/ci/test-msys2.sh
+++ b/.gitlab/ci/test-msys2.sh
@@ -19,7 +19,8 @@ pacman --noconfirm -S --needed \
     mingw-w64-$MSYS2_ARCH-libpng \
     mingw-w64-$MSYS2_ARCH-libtiff \
     mingw-w64-$MSYS2_ARCH-meson \
-    mingw-w64-$MSYS2_ARCH-toolchain
+    mingw-w64-$MSYS2_ARCH-toolchain \
+    mingw-w64-$MSYS2_ARCH-libxslt
 
 meson --buildtype debug \
     -Dx11=false \