decoder/OpusDecoderPlugin: fix build failure due to missing stdio.h include

src/decoder/OpusDecoderPlugin.cxx

@@ -40,6 +40,7 @@
 #include <glib.h>
 
 #include <string.h>
+#include <stdio.h>
 
 static constexpr opus_int32 opus_sample_rate = 48000;