gst-build: Only use gstreamer runners for windows jobs

gst-build: Only use gstreamer runners for windows jobs

Till we can update the container image to the Feb 11 security update,
all x86 executables will crash because of:

https://support.microsoft.com/en-us/help/4542617/you-might-encounter-issues-when-using-windows-server-containers-with-t

So restrict to the gstreamer runners that are running an older Windows
version. For example:

```
subprojects\gstreamer\gst\parse\meson.build:10:0: ERROR: Command
  "c:\python38\python.exe
  C:\builds\thaytan\gst-plugins-good\gst-build\subprojects\gstreamer\gst\parse\get_flex_version.py
  C:\builds\thaytan\gst-plugins-good\gst-build\subprojects\win-flex-bison-binaries\win_flex.exe"
  failed with status 1.
```

https://gitlab.freedesktop.org/thaytan/gst-plugins-good/-/jobs/2066909

```
meson.build:1:0: ERROR: Executables created by c compiler cl are not runnable.
```

https://gitlab.freedesktop.org/nirbheek/gst-ci/-/jobs/2070394