Try this:
$> git clone https://github.com/wf9a5m75/ionic-native
$> cd ionic-native
$> node -v
v9.3.0 <-- important!
$> npm install
$> npm run build
$> cd (your project path)
$> npm uninstall @ionic-native/core @ionic-native/google-maps
$> npm install (path to ionic-native directory)/dist/\@ionic-native/core
$> npm install (path to ionic-native directory)/dist/\@ionic-native/google-maps
$> ionic cordova run android