gitlab-ci: fix dist-installer-weekly job.

Since dist-installer-weekly doesn't depend on gimp-debian-x64 anymore, we need
to grab the config.h from one of the other dependencies. Let's use the one from
gimp-win-a64 (though it could have been any other Windows build job).

Fixes:

> Get-Content : Cannot bind argument to parameter 'Path' because it is an empty string.
> At C:\_r\_builds\vJWzEqDv\0\GNOME\gimp\build\windows\gitlab-ci\4_dist-gimp-inno.ps1:13 char:39
> +     $GIMP_VERSION = Get-Content -Path "$CONFIG_PATH"         | Select ...
> +                                       ~~~~~~~~~~~~~~
>     + CategoryInfo          : InvalidData: (:) [Get-Content], ParameterBindingValidationException
>     + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Microsoft.PowerShell.Commands.GetC
>    ontentCommand

.gitlab-ci.yml

@@ -705,6 +705,8 @@ gimp-win-a64:
     - _install-a64
     - _build-a64/build/windows/installer/
     - _build-a64/meson-*/
+    # Needed by 4_dist-gimp-inno.ps1 in dist-installer-weekly
+    - _build-a64/config.h
   cache:
     paths:
     - _ccache/
@@ -746,6 +748,8 @@ packaging-win-a64:
     - gimp-a64
     # Just passing-through splash and language files for the Windows installer.
     - _build-a64/build/windows/installer/
+    # Needed by 4_dist-gimp-inno.ps1 in dist-installer-weekly
+    - _build-a64/config.h
     - done-dll.list
   needs: ["gimp-win-a64"]