Use LiveKit's Rust SDK on Linux while continue using Swift SDK on Mac (#21550)

Similar to #20826 but keeps the Swift implementation. There were quite a
few changes in the `call` crate, and so that code now has two variants.

Closes #13714

Release Notes:

- Added preliminary Linux support for voice chat and viewing
screenshares.

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/zed/build.rs

@@ -13,6 +13,14 @@ fn main() {
             println!("cargo:rustc-link-arg=-Wl,-rpath,@executable_path");
         }
 
+        if std::env::var("ZED_BUNDLE").ok().as_deref() == Some("true") {
+            // Find WebRTC.framework in the Frameworks folder when running as part of an application bundle.
+            println!("cargo:rustc-link-arg=-Wl,-rpath,@executable_path/../Frameworks");
+        } else {
+            // Find WebRTC.framework as a sibling of the executable when running outside of an application bundle.
+            println!("cargo:rustc-link-arg=-Wl,-rpath,@executable_path");
+        }
+
         // Weakly link ReplayKit to ensure Zed can be used on macOS 10.15+.
         println!("cargo:rustc-link-arg=-Wl,-weak_framework,ReplayKit");