build: allow disabling vapoursynth completely

It's possible to build vf_vapoursynth with either the Python or Lua
backend (or both or none). The check for the vapoursynth core itself was
hidden away and couldn't be disabled, which would link mpv with
vapoursynth even if all backends were disabled.

Rearrange the checks so that the core will be disabled if no backend is
found (or both are disabled). This duplicates the check for
vapoursynth.pc, but since it's trivial, this is not that bad.

1 files changed, 8 insertions, 7 deletions

diff --git a/wscript b/wscript
index 981f55b163..1b1372ee5a 100644
--- a/wscript
+++ b/wscript
@@ -356,18 +356,19 @@ iconv support use --disable-iconv.",
         'desc': 'LCMS2 support',
         'func': check_pkg_config('lcms2', '>= 2.6'),
     }, {
-        'name': 'vapoursynth-core',
-        'desc': 'VapourSynth filter bridge (core)',
-        'func': check_pkg_config('vapoursynth >= 24'),
-    }, {
         'name': '--vapoursynth',
         'desc': 'VapourSynth filter bridge (Python)',
-        'deps': ['vapoursynth-core'],
-        'func': check_pkg_config('vapoursynth-script >= 23'),
+        'func': check_pkg_config('vapoursynth',        '>= 24',
+                                 'vapoursynth-script', '>= 23'),
     }, {
         'name': '--vapoursynth-lazy',
         'desc': 'VapourSynth filter bridge (Lazy Lua)',
-        'deps': ['vapoursynth-core', 'lua'],
+        'deps': ['lua'],
+        'func': check_pkg_config('vapoursynth',        '>= 24'),
+    }, {
+        'name': 'vapoursynth-core',
+        'desc': 'VapourSynth filter bridge (core)',
+        'deps_any': ['vapoursynth', 'vapoursynth-lazy'],
         'func': check_true,
     }, {
         'name': '--libarchive',