ci: use ffmpeg 4.4 instead of master

wang-bin · wang-bin · commit bcd9d05bdcf3 · 2021-05-04T20:38:15.000+08:00
master major version is 5, new abi
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -7,7 +7,7 @@ on:
   repository_dispatch:
 
 env:
-  FF_VER: master
+  FF_VER: 4.4
   LLVM_VER: 12
   NDK_VERSION: r22
   NINJA_STATUS: '[%f/%t %e %r]'
