meson: Cleanup plugin build script

lib/gst/plugin/meson.build

@@ -4,6 +4,8 @@ gst_clapper_plugin_args = [
   '-DHAVE_CONFIG_H',
   '-DGST_USE_UNSTABLE_API',
 ]
+
+gst_clapper_sink_dep = dependency('', required: false)
 gtk4_dep = dependency('gtk4', version: '>=4.6.0', required: false)
 
 gmodule_dep = dependency('gmodule-2.0',
@@ -20,12 +22,13 @@ gst_clapper_plugin_deps = [
   gmodule_dep,
 ]
 
+build_gst_plugin = not get_option('gst-plugin').disabled()
 foreach dep : gst_clapper_plugin_deps
   if not dep.found()
     if get_option('gst-plugin').enabled()
       error('GStreamer plugin was enabled, but required dependencies were not found')
     endif
-    subdir_done()
+    build_gst_plugin = false
   endif
 endforeach
 
@@ -42,17 +45,19 @@ gst_clapper_plugin_sources = [
   'gstclapperimporterloader.c',
 ]
 
-gst_clapper_sink_dep = declare_dependency(
-  link_with: library('gstclapper',
-    gst_clapper_plugin_sources,
-    c_args: gst_clapper_plugin_args,
+if build_gst_plugin
+  gst_clapper_sink_dep = declare_dependency(
+    link_with: library('gstclapper',
+      gst_clapper_plugin_sources,
+      c_args: gst_clapper_plugin_args,
+      include_directories: configinc,
+      dependencies: gst_clapper_plugin_deps,
+      install: true,
+      install_dir: gst_plugins_libdir,
+    ),
     include_directories: configinc,
     dependencies: gst_clapper_plugin_deps,
-    install: true,
-    install_dir: gst_plugins_libdir,
-  ),
-  include_directories: configinc,
-  dependencies: gst_clapper_plugin_deps,
-)
+  )
+endif
 
 subdir('importers')