[v6.5.4] Build path not correct in package.json 

when running npm run build on the latest version i get:

```
> @geoext/openlayers-legacy@6.5.4 build
> ./build-openlayers-legacy.sh

'.' is not recognized as an internal or external command,
operable program or batch file.
```

updating package.json:6 to:
`"build": "build-openlayers-legacy.sh",`
 fixes the issue