build: add separate spice-protocol config option

When implementing spice vdagent protocol in qemu we only need the
spice-protocol package for that, spice-server is not needed.  So
go split those two build dependencies.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20210519053940.1888907-1-kraxel@redhat.com
Message-Id: <20210519053940.1888907-2-kraxel@redhat.com>
diff --git a/meson.build b/meson.build
index 1559e8d..632b380 100644
--- a/meson.build
+++ b/meson.build
@@ -458,11 +458,15 @@
 endif
 spice = not_found
 spice_headers = not_found
+spice_protocol = not_found
 if 'CONFIG_SPICE' in config_host
   spice = declare_dependency(compile_args: config_host['SPICE_CFLAGS'].split(),
                              link_args: config_host['SPICE_LIBS'].split())
   spice_headers = declare_dependency(compile_args: config_host['SPICE_CFLAGS'].split())
 endif
+if 'CONFIG_SPICE_PROTOCOL' in config_host
+  spice_protocol = declare_dependency(compile_args: config_host['SPICE_PROTOCOL_CFLAGS'].split())
+endif
 rt = cc.find_library('rt', required: false)
 libdl = not_found
 if 'CONFIG_PLUGIN' in config_host