Swap clone script with before_build

appveyor.yml

@@ -1,7 +1,7 @@
 image: 'Visual Studio 2017'
-clone_script:
-- cmd: >-
-    git clone -q --branch=%APPVEYOR_REPO_BRANCH% https://github.com/%APPVEYOR_REPO_NAME%.git %APPVEYOR_BUILD_FOLDER%
-    cd %APPVEYOR_BUILD_FOLDER%
-    git checkout -qf %APPVEYOR_REPO_COMMIT%
-    git submodule update --init --recursive
+
+configuration:
+  - Release
+
+before_build:
+- cmd: git submodule update --init --recursive