meson: check for dav1d dep

Needed to build dav1d-sys which is required by the dav1d decoder plugin.

Exclude the plugin if the dep isn't found, preventing the build to fail.

cargo.py

@@ -7,7 +7,7 @@ import shutil
 import subprocess
 import sys
 
-meson_build_dir, meson_current_source_dir, meson_build_root, target, ext = sys.argv[1:]
+meson_build_dir, meson_current_source_dir, meson_build_root, target, ext, exclude = sys.argv[1:]
 
 cargo_target_dir = os.path.join(meson_build_dir, 'target')
 
@@ -27,10 +27,15 @@ env['PKG_CONFIG_PATH'] = ':'.join(pkg_config_path)
 
 # cargo build
 cargo_cmd = ['cargo', 'build', '--manifest-path',
-             os.path.join(meson_current_source_dir, 'Cargo.toml')]
+             os.path.join(meson_current_source_dir, 'Cargo.toml'),
+             '--workspace']
 if target == 'release':
     cargo_cmd.append('--release')
 
+for e in exclude.split(','):
+    cargo_cmd.append('--exclude')
+    cargo_cmd.append(e)
+
 try:
     subprocess.run(cargo_cmd, env=env, check=True)
 except subprocess.SubprocessError:

meson.build

@@ -25,7 +25,6 @@ plugins_rep = {
   'gst-plugin-audiofx': 'libgstrsaudiofx',
   'gst-plugin-cdg': 'libgstcdg',
   'gst-plugin-closedcaption': 'libgstrsclosedcaption',
-  'gst-plugin-dav1d': 'libgstrsdav1d',
   'gst-plugin-fallbackswitch': 'libgstfallbackswitch',
   'gst-plugin-file': 'libgstrsfile',
   'gst-plugin-flv': 'libgstrsflv',
@@ -38,6 +37,14 @@ plugins_rep = {
   'gst-plugin-togglerecord': 'libgsttogglerecord',
 }
 
+exclude = []
+
+if dependency('dav1d', required : false).found()
+  plugins_rep += {'gst-plugin-dav1d' : 'libgstrsdav1d'}
+else
+  exclude += ['gst-plugin-dav1d']
+endif
+
 output = []
 
 foreach p, lib : plugins_rep
@@ -86,7 +93,8 @@ rs_plugins = custom_target('gst-plugins-rs',
     meson.current_source_dir(),
     meson.build_root(),
     target,
-    ext])
+    ext,
+    ','.join(exclude)])
 
 # FIXME: raises a warning as the target has multiple outputs and meson will use
 # only the first one. All the plugins have the same basedir, hence