Fix out of source tree builds of libmpcodecs.

diff --git a/configure b/configure
index 5734da3..0891228 100755 (executable)
--- a/configure
+++ b/configure
@@ -3122,6 +3122,8 @@ if enabled source_path_used; then
         libavdevice
         libavfilter
         libavfilter/$arch
+        libavfilter/libmpcodecs
+        libavfilter/libmpcodecs/libvo
         libavformat
         libavutil
         libavutil/$arch