I solved the problem by using CDN mapbox in index.html :
<link rel="stylesheet" href="https://api.tiles.mapbox.com/mapbox-gl-js/v0.41.0/mapbox-gl.css">
<script src="https://api.tiles.mapbox.com/mapbox-gl-js/v0.41.0/mapbox-gl.js"></script>
And in my typescript file :
import ...
declare var mapboxgl;
import ...