[Wasm] Set SWIFT_THREADING_PACKAGE explicitly since no SWIFT_HOST_VARIANT_SDK

Author: kateinoigakukun

cmake/caches/Runtime-WASI-wasm32.cmake

@@ -28,6 +28,7 @@ set(SWIFT_STDLIB_ENABLE_THINCMO YES CACHE BOOL "")
 set(SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER YES CACHE BOOL "")
 
 set(SWIFT_STDLIB_SINGLE_THREADED_CONCURRENCY TRUE CACHE BOOL "")
+set(SWIFT_THREADING_PACKAGE TRUE CACHE STRING "none")
 
 set(SWIFT_STDLIB_SUPPORTS_BACKTRACE_REPORTING FALSE CACHE BOOL "")
 set(SWIFT_STDLIB_HAS_DLADDR FALSE CACHE BOOL "")