Add test for new relative-path option.
Add test for new relative-path option.

Refs #12438

mvdriel/cakephp,tenkoma/cakephp,CakeDC/cakephp,tenkoma/cakephp,tenkoma/cakephp,garethellis36/cakephp,dakota/cakephp,ADmad/cakephp,ADmad/cakephp,garethellis36/cakephp,ndm2/cakephp,garethellis36/cakephp,ndm2/cakephp,mvdriel/cakephp,CakeDC/cakephp,CakeDC/cakephp,garethellis36/cakephp,dakota/cakephp,cakephp/cakephp,petteyg/cakephp,tenkoma/cakephp,cakephp/cakephp,mvdriel/cakephp,petteyg/cakephp,petteyg/cakephp,ADmad/cakephp,cakephp/cakephp,petteyg/cakephp,cakephp/cakephp,ADmad/cakephp,mvdriel/cakephp,dakota/cakephp,dakota/cakephp,CakeDC/cakephp,ndm2/cakephp,ndm2/cakephp