mac: Statically link ffms2

This is to make sure we're building the git version that fixes the
PAFF seeking regression and contains the workarounds for VPX/AV1.

Author: arch1t3cht

.github/workflows/ci.yml

@@ -53,13 +53,13 @@ jobs:
             name: macOS Debug,
             os: macos-latest,
             buildtype: debugoptimized,
-            args: -Ddefault_library=static -Dbuild_osx_bundle=true -Dlocal_boost=true
+            args: -Ddefault_library=static -Dbuild_osx_bundle=true -Dlocal_boost=true --force-fallback-for=ffms2
           }
           - {
             name: macOS Release,
             os: macos-latest,
             buildtype: release,
-            args: -Ddefault_library=static -Dbuild_osx_bundle=true -Dlocal_boost=true
+            args: -Ddefault_library=static -Dbuild_osx_bundle=true -Dlocal_boost=true --force-fallback-for=ffms2
           }
 
     steps: