cmake: Add ffmpeg to appveyor vcpkg cache.

Now that the initial vcpkg cache has been populated in appveyor, we can
build ffmpeg to add to it without going over the job limit.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

CMakeLists.txt

@@ -15,8 +15,10 @@ set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
 
 set(VCPKG_DEPS zlib libpng SDL2 SFML gettext wxWidgets)
 
-if(NOT DEFINED ENV{APPVEYOR})
-    # job goes over time limit if building ffmpeg
+# appveyor job goes over time limit if building ffmpeg during initial cache
+# generation. So build initial cache without ffmpeg.
+#if(NOT DEFINED ENV{APPVEYOR})
+if(1)
     list(APPEND VCPKG_DEPS ffmpeg)
 endif()