Hi @Corentin,
Checked your project and the workdir seems to be good; the issue seems to be the Ionic/Cordova CLI version. You most likely used Cordova v7 and Ionic v3, but on the stack which you selected (the Hybrid one) Cordova v6 and Ionic CLI v2 are preinstalled.
I switched your project to the Visual Studio for Mac stack, which has Cordova v7 and Ionic v3 preinstalled and the build succeeded.
Alternatively you can use the related steps’ version inputs (in this case the Ionic Archive step’s) to specify a version for the CLIs if you’d want to keep using the Hybrid/Xcode 8 stack:
Let us know if you have any questions, and Happy Building! 