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/livekit_client_macos/build.rs

@@ -0,0 +1,185 @@
+use serde::Deserialize;
+use std::{
+    env,
+    path::{Path, PathBuf},
+    process::Command,
+};
+
+const SWIFT_PACKAGE_NAME: &str = "LiveKitBridge";
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SwiftTargetInfo {
+    pub triple: String,
+    pub unversioned_triple: String,
+    pub module_triple: String,
+    pub swift_runtime_compatibility_version: String,
+    #[serde(rename = "librariesRequireRPath")]
+    pub libraries_require_rpath: bool,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SwiftPaths {
+    pub runtime_library_paths: Vec<String>,
+    pub runtime_library_import_paths: Vec<String>,
+    pub runtime_resource_path: String,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct SwiftTarget {
+    pub target: SwiftTargetInfo,
+    pub paths: SwiftPaths,
+}
+
+const MACOS_TARGET_VERSION: &str = "10.15.7";
+
+fn main() {
+    if cfg!(all(
+        target_os = "macos",
+        not(any(test, feature = "test-support", feature = "no-webrtc")),
+    )) {
+        let swift_target = get_swift_target();
+
+        build_bridge(&swift_target);
+        link_swift_stdlib(&swift_target);
+        link_webrtc_framework(&swift_target);
+
+        // Register exported Objective-C selectors, protocols, etc when building example binaries.
+        println!("cargo:rustc-link-arg=-Wl,-ObjC");
+    }
+}
+
+fn build_bridge(swift_target: &SwiftTarget) {
+    println!("cargo:rerun-if-env-changed=MACOSX_DEPLOYMENT_TARGET");
+    println!("cargo:rerun-if-changed={}/Sources", SWIFT_PACKAGE_NAME);
+    println!(
+        "cargo:rerun-if-changed={}/Package.swift",
+        SWIFT_PACKAGE_NAME
+    );
+    println!(
+        "cargo:rerun-if-changed={}/Package.resolved",
+        SWIFT_PACKAGE_NAME
+    );
+
+    let swift_package_root = swift_package_root();
+    let swift_target_folder = swift_target_folder();
+    let swift_cache_folder = swift_cache_folder();
+    if !Command::new("swift")
+        .arg("build")
+        .arg("--disable-automatic-resolution")
+        .args(["--configuration", &env::var("PROFILE").unwrap()])
+        .args(["--triple", &swift_target.target.triple])
+        .args(["--build-path".into(), swift_target_folder])
+        .args(["--cache-path".into(), swift_cache_folder])
+        .current_dir(&swift_package_root)
+        .status()
+        .unwrap()
+        .success()
+    {
+        panic!(
+            "Failed to compile swift package in {}",
+            swift_package_root.display()
+        );
+    }
+
+    println!(
+        "cargo:rustc-link-search=native={}",
+        swift_target.out_dir_path().display()
+    );
+    println!("cargo:rustc-link-lib=static={}", SWIFT_PACKAGE_NAME);
+}
+
+fn link_swift_stdlib(swift_target: &SwiftTarget) {
+    for path in &swift_target.paths.runtime_library_paths {
+        println!("cargo:rustc-link-search=native={}", path);
+    }
+}
+
+fn link_webrtc_framework(swift_target: &SwiftTarget) {
+    let swift_out_dir_path = swift_target.out_dir_path();
+    println!("cargo:rustc-link-lib=framework=WebRTC");
+    println!(
+        "cargo:rustc-link-search=framework={}",
+        swift_out_dir_path.display()
+    );
+    // Find WebRTC.framework as a sibling of the executable when running tests.
+    println!("cargo:rustc-link-arg=-Wl,-rpath,@executable_path");
+    // Find WebRTC.framework in parent directory of the executable when running examples.
+    println!("cargo:rustc-link-arg=-Wl,-rpath,@executable_path/..");
+
+    let source_path = swift_out_dir_path.join("WebRTC.framework");
+    let deps_dir_path =
+        PathBuf::from(env::var("OUT_DIR").unwrap()).join("../../../deps/WebRTC.framework");
+    let target_dir_path =
+        PathBuf::from(env::var("OUT_DIR").unwrap()).join("../../../WebRTC.framework");
+    copy_dir(&source_path, &deps_dir_path);
+    copy_dir(&source_path, &target_dir_path);
+}
+
+fn get_swift_target() -> SwiftTarget {
+    let mut arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+    if arch == "aarch64" {
+        arch = "arm64".into();
+    }
+    let target = format!("{}-apple-macosx{}", arch, MACOS_TARGET_VERSION);
+
+    let swift_target_info_str = Command::new("swift")
+        .args(["-target", &target, "-print-target-info"])
+        .output()
+        .unwrap()
+        .stdout;
+
+    serde_json::from_slice(&swift_target_info_str).unwrap()
+}
+
+fn swift_package_root() -> PathBuf {
+    env::current_dir().unwrap().join(SWIFT_PACKAGE_NAME)
+}
+
+fn swift_target_folder() -> PathBuf {
+    let target = env::var("TARGET").unwrap();
+    env::current_dir()
+        .unwrap()
+        .join(format!("../../target/{target}/{SWIFT_PACKAGE_NAME}_target"))
+}
+
+fn swift_cache_folder() -> PathBuf {
+    let target = env::var("TARGET").unwrap();
+    env::current_dir()
+        .unwrap()
+        .join(format!("../../target/{target}/{SWIFT_PACKAGE_NAME}_cache"))
+}
+
+fn copy_dir(source: &Path, destination: &Path) {
+    assert!(
+        Command::new("rm")
+            .arg("-rf")
+            .arg(destination)
+            .status()
+            .unwrap()
+            .success(),
+        "could not remove {:?} before copying",
+        destination
+    );
+
+    assert!(
+        Command::new("cp")
+            .arg("-R")
+            .args([source, destination])
+            .status()
+            .unwrap()
+            .success(),
+        "could not copy {:?} to {:?}",
+        source,
+        destination
+    );
+}
+
+impl SwiftTarget {
+    fn out_dir_path(&self) -> PathBuf {
+        swift_target_folder()
+            .join(&self.target.unversioned_triple)
+            .join(env::var("PROFILE").unwrap())
+    }
+}