fix: System.register __filename format on windows boxes
fix: System.register __filename format on windows boxes

systemjs/builder,systemjs/builder,matthewbauer/builder,synaptek/builder,douglasduteil/builder,alexandr2110pro/builder,buddhike/builder,tonytanger/builder,synaptek/builder,robwormald/builder,alexandr2110pro/builder,jrauschenbusch/builder,lookfirst/builder,buddhike/builder,tonytanger/builder,Psvensso/builder,richardTowers/builder,jrauschenbusch/builder,alexisvincent/builder,Psvensso/builder,robwormald/builder,whitneyit/builder,douglasduteil/builder,alexisvincent/builder,ahmedshuhel/builder,JeroenVinke/builder,systemjs/builder,richardTowers/builder,Munter/builder,ahmedshuhel/builder,matthewbauer/builder,Munter/builder,JeroenVinke/builder,jrauschenbusch/builder,lookfirst/builder,whitneyit/builder,alexisvincent/builder