plugins: allow plugins to be enabled on windows

allow plugins to be enabled in the configure script on windows. Also,
add the qemu_plugin_api.lib to the installer.

Signed-off-by: Greg Manning <gmanning@rapitasystems.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231102172053.17692-5-gmanning@rapitasystems.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
[AJB: add check for dlltool to configure]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231106185112.2755262-17-alex.bennee@linaro.org>