[gimp/wip/Jehan/native-win64-build] Add back gtk-doc.

[Jehan <jehanp src gnome org>]

commit 5cdde67115458cdaec906c1dd5c73c2d905ab744
Author: Jehan <jehan girinstud io>
Date:   Wed May 5 22:09:30 2021 +0200

    Add back gtk-doc.

 build/windows/gitlab-ci/build-gimp-msys2.sh | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build/windows/gitlab-ci/build-gimp-msys2.sh b/build/windows/gitlab-ci/build-gimp-msys2.sh
index 778b6daec9..0ffb8a837c 100644
--- a/build/windows/gitlab-ci/build-gimp-msys2.sh
+++ b/build/windows/gitlab-ci/build-gimp-msys2.sh
@@ -44,6 +44,7 @@ pacman --noconfirm -S --needed \
     mingw-w64-$MSYS2_ARCH-gobject-introspection-runtime \
     mingw-w64-$MSYS2_ARCH-graphviz \
     mingw-w64-$MSYS2_ARCH-gtk3 \
+    mingw-w64-$MSYS2_ARCH-gtk-doc \
     mingw-w64-$MSYS2_ARCH-iso-codes \
     mingw-w64-$MSYS2_ARCH-json-c \
     mingw-w64-$MSYS2_ARCH-json-glib \