Add slow tag

Author: eregon

spec/tags/truffle/launcher_tags.txt

@@ -62,3 +62,4 @@ slow:The launcher does not create context on --version and -v
 aot(no sulong):The launcher 'gem' in `RbConfig::CONFIG['bindir']` directory runs when symlinked
 aot(no sulong):The launcher 'gem' in `RbConfig::CONFIG['extra_bindirs'][0]` directory runs when symlinked
 aot(no sulong):The launcher 'gem' in `RbConfig::CONFIG['extra_bindirs'][1]` directory runs when symlinked
+slow:The launcher applies Truffle options