apple binaries are linked against the system libexpat library

[tanersener]

Description
When apple platform (ios, macos, tvos) build scripts enable an external library that requires expat, build scripts are linked against the libexpat system library that comes with the newer SDK versions.

First reported in https://github.com/tanersener/ffmpeg-kit-test/issues/18

Expected behavior
Linked libraries should work on all platforms.

Current behavior
Unfortunately, older system runtimes e.g. iOS 13.5 don't have libexpat. So, they fail to load ffmpeg libraries.

To Reproduce

1. Run ios.sh by enabling either fontconfig or libass
2. Start your application on iOS SDK 13.5

Logs

dyld: Library not loaded: /usr/lib/libexpat.1.dylib
  Referenced from: /Users/taner/Library/Developer/CoreSimulator/Devices/5D5AD397-2408-4E70-9308-28E80DF86065/data/Containers/Bundle/Application/2D2FC5FC-E951-4721-9338-6B4BE0F3C7AB/FFmpegKitIOS.app/Frameworks/libavdevice.framework/libavdevice
  Reason: image not found
dyld: launch, loading dependent libraries

Environment

• Platform: iOS/macOS/tvOS
• Architecture: armv7, armv7s, arm64, arm64-mac-catalyst, arm64-simulator, arm64e, i386, x86-64, x86-64-mac-catalyst
• Version: v4.5.1 and v4.5.1.LTS
• Source branch: main
• Xcode version: 13.2.1
• Cocoapods version: 1.11.2

Other
This happens because Apple platforms try to load dynamic libraries first. Since there is a dynamic libexpat.1.dylib library found in search paths, they ignore the static binary built by ios.sh, macos.sh and tvos.sh.

This behaviour is explained in QA1393.

[tanersener]

This bug affects video, full and full-gpl packages of v4.5.1 and v4.5.1.LTS

[tanersener]

I patched Apple platform (ios, macos, tvos) releases v4.5.1 and v4.5.1.LTS with the fix for this issue.

Please clean you pod cache and run pod install again if you encounter the error described in the first post.

pod cache clean ffmpeg-kit-ios-full