Update build server scripts

Fix the build server scripts for Linux and Android by checking out the
wireguard-go submodule.

Author: MarkusPettersson98

ci/buildserver-build-android.sh

@@ -65,6 +65,7 @@ function checkout_ref {
     git reset --hard
     git checkout "$ref"
     git submodule update
+    git submodule update --init --recursive --depth=1 wireguard-go-rs || true
     git clean -df
 }
 

ci/buildserver-build.sh

@@ -163,6 +163,7 @@ function checkout_ref {
     git reset --hard
     git checkout "$ref"
     git submodule update
+    git submodule update --init --recursive --depth=1 wireguard-go-rs || true
     git clean -df
 }