Thx @AaronSterling … just checked, I already created that src/service-worker.js file back then when ionic-app-scripts 0.0.38 was introduced 
Gonna upgrade to last ionic-angular, app-scripts, node, npm…next days gonna be a lot of fun 
Update node 8 and npm 5 locally and, because why not, on my staging server…it works just fine, migration was super quick without any problem, quite cool. again thx for the confirmation.
ionic build is not working after upgrading npm5.
Create a new topic on that. Include the exact command you are executing, the error message you are getting and your ionic info output.
ionic build is working fine with npm 5.0.2 .
Thanks for your suggestion