+ register the wasip1threads target in the compiler

compiler/systems/t_wasi.pas

@@ -398,6 +398,9 @@ initialization
   RegisterTarget(system_wasm32_wasip1_info);
   RegisterImport(system_wasm32_wasip1, timportlibwasi);
   RegisterExport(system_wasm32_wasip1, texportlibwasi);
+  RegisterTarget(system_wasm32_wasip1threads_info);
+  RegisterImport(system_wasm32_wasip1threads, timportlibwasi);
+  RegisterExport(system_wasm32_wasip1threads, texportlibwasi);
   RegisterLinker(ld_int_wasi,TInternalLinkerWasi);
   RegisterLinker(ld_wasi, tlinkerwasi);
   RegisterRes(res_wasm_info,TWinLikeResourceFile);