Only use test wrapper-script if host is MinGW

Currently it fails if the executable extension is .exe, but wine isn't
available (e.g. on Cygwin)

Possibly the check to use this wrapper should be even more restrictive
e.g. checking if cross-building and/or if wine is available.
3 jobs for master in 9 minutes and 30 seconds
latest
Status Job ID Name Coverage
  Build
passed mingw-build #239183

00:09:13

passed shared-build #239181

00:04:31

passed static-build #239182

00:09:30