Replace xcodebuild with cc crate in build.rs

The pomace Objective-C files are compiled using the cc crate instead of
invoking xcodebuild directly. This removes the hard dependency on
Xcode.app, enabling builds with just Apple Command Line Tools and in
sandboxed environments like Nix.

Changes:
- Use cc::Build to compile each pomace .m file individually
- Add -fobjc-arc, -fobjc-weak, -fno-common flags to match Xcode's
  build settings
- Add -include Foundation/Foundation.h for targets that import C-only
  frameworks (e.g. CoreAudio) but use Foundation types
- Use CC env var / cc crate compiler detection for clang_rt discovery
  instead of hardcoded /usr/bin/clang
- Try SDKROOT env var before falling back to xcrun for Mac Catalyst
- Preserve all platform-conditional target gating from the original

Framework linking is unchanged — cidre's Rust source handles it via
#[link] attributes, same as before.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: itskhalil

cidre/Cargo.toml

@@ -280,6 +280,9 @@ visionos_26_1 = ["visionos_26_0"]
 
 # end of deployment targets
 
+[build-dependencies]
+cc = "1"
+
 [dependencies]
 
 tokio = { optional = true, version = "1", default-features = false, features = ["macros", "rt", "rt-multi-thread", "time", "net", "process", "io-util"] }