Install composer deps with -o flag to fix an autoloading error

For an yet unknown reason, composer suddenly fails to load the
UrlLinker class if dependencies haven't been installed with the
optimize flag.

Ref #697

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

krankerl.toml

 [package]
 before_cmds = [
-	"composer install --no-dev",
+	"composer install --no-dev -o",
 	"npm install --deps",
 	"npm run build",
 ]