configure, meson: replace VSS SDK checks and options with --enable-vss-sdk

The VSS headers are part of standard MS VS SDK, at least since version
15, and probably before that.

They are also included with MinGW, although currently broken.

Let's streamline a bit the options, by not making it so special, and
instead rely on proper system headers configuration or user
--extra-cxxflags. This still requires some extra step to cross-build
with MinGW as described in the meson.build file now.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[Use a "feature"-type option. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
5 files changed