meson: use prefer_static option

The option is new in Meson 0.63 and removes the need to pass "static:
true" to all dependency and find_library invocation.  Actually cleaning
up the invocations is left for a separate patch.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qga/meson.build

@@ -22,7 +22,7 @@ have_qga_vss = get_option('qga_vss') \
     Then run configure with: --extra-cxxflags="-isystem /path/to/vss/inc/win2003"''') \
   .require(midl.found() or widl.found(),
            error_message: 'VSS support requires midl or widl') \
-  .require(not enable_static,
+  .require(not get_option('prefer_static'),
            error_message: 'VSS support requires dynamic linking with GLib') \
   .allowed()