meson: don't access 'cxx' object without checking cpp lang

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20260210173355.776365-1-berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

meson.build

@@ -3200,7 +3200,7 @@ if host_os == 'windows'
 endif
 
 # Detect if ConvertStringToBSTR has been defined in _com_util namespace
-if host_os == 'windows'
+if host_os == 'windows' and 'cpp' in all_languages
   has_convert_string_to_bstr = cxx.links('''
     #include <comutil.h>
     int main() {