appveyor: use the build.cmd script to install streamlink, so that the sdk can be used if required
appveyor: use the build.cmd script to install streamlink, so that the sdk can be used if required

beardypig/streamlink,javiercantero/streamlink,back-to/streamlink,bastimeyer/streamlink,streamlink/streamlink,mmetak/streamlink,streamlink/streamlink,chhe/streamlink,mmetak/streamlink,wlerin/streamlink,bastimeyer/streamlink,gravyboat/streamlink,melmorabity/streamlink,wlerin/streamlink,back-to/streamlink,javiercantero/streamlink,beardypig/streamlink,chhe/streamlink,melmorabity/streamlink,gravyboat/streamlink