[FFmpeg-cvslog] configure: add libplacebo to help message

[Zhao Zhili]

ffmpeg | branch: master | Zhao Zhili <quinkblack at foxmail.com> | Thu Jan 27 13:01:43 2022 +0800| [2b15acb96aa011a0356d9dafe60e8bb2bdebf363] | committer: Lynne

configure: add libplacebo to help message

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2b15acb96aa011a0356d9dafe60e8bb2bdebf363
---

 configure | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure b/configure
index 493493b4c5..5b19a35f59 100755
--- a/configure
+++ b/configure
@@ -255,6 +255,7 @@ External library support:
   --enable-libopenvino     enable OpenVINO as a DNN module backend
                            for DNN based filters like dnn_processing [no]
   --enable-libopus         enable Opus de/encoding via libopus [no]
+  --enable-libplacebo      enable libplacebo library [no]
   --enable-libpulse        enable Pulseaudio input via libpulse [no]
   --enable-librabbitmq     enable RabbitMQ library [no]
   --enable-librav1e        enable AV1 encoding via rav1e [no]