Fix Objective-C linking

[ladvoc]

The ObjC categories in libwebrtc.a (e.g. NSString (StdString)) export no symbols, so the linker drops them and macOS/iOS binaries abort at startup:

+[NSString stringForStdString:]: unrecognized selector sent to class

The usual fix, -ObjC (currently documented in the README as required for consumers), can't be applied at the crate level since Cargo doesn't propagate link args to dependent crates. Instead, merge all obj/sdk objects into one archive member when assembling libwebrtc.a, so the categories load together with the referenced SDK symbols and consumers need no flag as of the next prebuilt release.

After this merges, livekit-examples/rust-dev-client should be updated to remove the workaround.

[github-actions]

No changeset found

This PR modifies versioned packages but doesn't include a changeset. The following packages require a version bump:

• libwebrtc
• livekit
• livekit-ffi
• webrtc-sys

A package must be bumped when its own files change, and whenever a package it depends on is bumped (so downstream consumers get a matching release).

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[pblazej]

Works fine locally