test: disable Concurrency/Runtime/exclusivity.swift on WASI

Tests for crashes aren't available on WebAssembly/WASI since there's no way to intercept traps or crashes on this platform. Trapping causes the whole Wasm VM to shut down with no way to recover from within the test code.

Author: MaxDesiatov

test/Concurrency/Runtime/exclusivity.swift

@@ -5,6 +5,7 @@
 
 // REQUIRES: concurrency_runtime
 // UNSUPPORTED: back_deployment_runtime
+// UNSUPPORTED: OS=wasi
 
 // This test makes sure that:
 //