Incorrect warning when passing `-l` RTS option

When passing the `-l` RTS option to enable the eventlog, then cabal warns me about using `extra-libraries`, which is for the GHC option `-l`.

```
ghc-options: +RTS -l -RTS
```

I get the following warning

```
Warning: Instead of 'ghc-options: -l' use 'extra-libraries: '
```