Clone submodules for CI

appveyor.yml

@@ -67,6 +67,9 @@ matrix:
 # For simple configurations, instead of using the build matrix, you can simply set the
 # default-toolchain and default-host manually here.
 install:
+  #Download submodules
+  git submodule update --init --recursive
+
   #Rust install
   - appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
   - rustup-init -yv --default-toolchain %channel% --default-host %target%