ci/win32: add zlib

It should work out of the box, but upstream meson wrap is not robust in
this case.

ci/build-win32.ps1

@@ -72,8 +72,8 @@ Copy-Item -Path "wrapdb_luajit/subprojects/packagefiles/luajit/*" `
 $projects = @(
     @{
         Path = "$subprojects/ffmpeg.wrap"
-        URL = "https://gitlab.freedesktop.org/gstreamer/meson-ports/ffmpeg.git"
-        Revision = "meson-6.1"
+        URL = "https://gitlab.freedesktop.org/kasper93/ffmpeg.git"
+        Revision = "mpv"
         Provides = @(
             "libavcodec = libavcodec_dep",
             "libavdevice = libavdevice_dep",
@@ -130,6 +130,7 @@ clone-recursive = true
 }
 
 meson setup build `
+    --force-fallback-for=zlib `
     -Ddefault_library=static `
     -Dlibmpv=true `
     -Dtests=true `