Refresh the use-path-in-usr-lib patch and the exec name and location

Upstream has decided to now ship the ffmpeg-mux executable as a binary
in /usr/bin. In order to keep the -plugins package Multiarch: Same, we
still need to ship it in /usr/lib/x86_64, although we now use the new
name to not diverge too much from upstream.

debian/patches/0003-Use-path-in-usr-lib.patch

@@ -6,18 +6,16 @@ Subject: Use path in /usr/lib
  plugins/obs-ffmpeg/obs-ffmpeg-mux.c | 4 ++++
  1 file changed, 4 insertions(+)
 
-diff --git a/plugins/obs-ffmpeg/obs-ffmpeg-mux.c b/plugins/obs-ffmpeg/obs-ffmpeg-mux.c
-index 9b65276..60b0b8b 100644
 --- a/plugins/obs-ffmpeg/obs-ffmpeg-mux.c
 +++ b/plugins/obs-ffmpeg/obs-ffmpeg-mux.c
-@@ -237,7 +237,11 @@ static void build_command_line(struct ffmpeg_muxer *stream, struct dstr *cmd,
+@@ -237,7 +237,11 @@
  		num_tracks++;
  	}
  
 +#ifdef FFMPEG_MUX_FIXED
 +	dstr_init_copy(cmd, FFMPEG_MUX_FIXED);
 +#else
- 	dstr_init_move_array(cmd, obs_module_file(FFMPEG_MUX));
+ 	dstr_init_move_array(cmd, os_get_executable_path_ptr(FFMPEG_MUX));
 +#endif
  	dstr_insert_ch(cmd, 0, '\"');
  	dstr_cat(cmd, "\" \"");