meson: add basic CI for MSVC

2 jobs for meson-ci-msvc in 58 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build
passed #6736213
docker windows 1809 gstreamer-windows
meson vs2017 amd64

00:00:58

passed #6736214
docker windows 1809 gstreamer-windows
meson vs2017 x86

00:00:57