Add patch to the CI build

.gitlab-ci.yml

@@ -5,6 +5,7 @@ build:
   variables:
     CADDY_TAG: $CI_COMMIT_TAG
   script:
+    - apt-get -yy update && apt-get -yy install patch
     - scripts/download "$(dirname $CI_PROJECT_URL)/caddy/-/archive/${CADDY_TAG}/caddy-${CADDY_TAG}.tar.gz"
     - mkdir -p "$GOPATH/src/github.com/mholt"
     - ln -s "$(pwd)/source" "$GOPATH/src/github.com/mholt/caddy"