How can I specify an angular environment on ionic build?

You can add a corresponding configuration entry in angular.json at ionic-cordova-build:

"ionic-cordova-build": {
  "builder": "@ionic/angular-toolkit:cordova-build",
  "options": {
    "browserTarget": "app:build"
  },
  "configurations": {
    "production": {
      "browserTarget": "app:build:production"
    },
    "staging": {
      "browserTarget": "app:build:staging"
    }
  }
},

$ ionic cordova run android --device -c staging

Note the difference from -c staging to -- -c=staging on ionic serve.

The configuration staging must exists under architect.build.configurations in the same file.