use eval-and-compile instead of eval-when-compile

[yyoncho]

The second one is causing issues when the package is downloaded from melpa

https://github.com/MaskRay/emacs-ccls/blob/914516d6ce7b1864b1dd479c79d682ea80916df9/ccls.el#L87

[MaskRay]

Thanks. Fixed. I don't know the difference, though..