meson: Enable building LV2

Note that I only support lilv 0.22+ for now, because it's simple and old
enough. If anyone needs to use the 0.16 support it will need to be
added.

ext/lv2/meson.build

@@ -0,0 +1,19 @@
+lv2_sources = [
+  'gstlv2.c',
+  'gstlv2filter.c',
+  'gstlv2source.c',
+  'gstlv2utils.c',
+]
+
+lv2_dep = dependency('lilv-0', version : '>= 0.22', required : false)
+if lv2_dep.found()
+  gstrsvg = library('gstlv2',
+    lv2_sources,
+    c_args : gst_plugins_bad_args,
+    link_args : noseh_link_args,
+    include_directories : [configinc],
+    dependencies : [gstaudio_dep, gstbase_dep, lv2_dep, mathlib],
+    install : true,
+    install_dir : plugins_install_dir,
+  )
+endif

ext/meson.build

@@ -25,7 +25,7 @@ subdir('kate')
 #subdir('ladspa')
 subdir('libde265')
 subdir('libmms')
-#subdir('lv2')
+subdir('lv2')
 #subdir('modplug')
 subdir('mpeg2enc')
 subdir('mplex')