llvm 16 optimizations lead to a segfault when seeking in opus files because
checks that could leave pos_max uninitialized are optimized away, leading
to out-of-bounds reads from the guard pages.

av_uninit() is complete batshittery:

https://marc.info/?l=openbsd-ports&m=170284868209618&w=2

Turns out the same commit has landed upstream:

https://github.com/FFmpeg/FFmpeg/commit/ab792634197e364ca1bb194f9abe36836e42f12d

Index: libavformat/utils.c
--- libavformat/utils.c.orig
+++ libavformat/utils.c
@@ -2146,7 +2146,7 @@ int ff_seek_frame_binary(AVFormatContext *s, int strea
                          int64_t target_ts, int flags)
 {
     const AVInputFormat *avif = s->iformat;
-    int64_t av_uninit(pos_min), av_uninit(pos_max), pos, pos_limit;
+    int64_t pos_min = 0, pos_max = 0, pos, pos_limit;
     int64_t ts_min, ts_max, ts;
     int index;
     int64_t ret;