Use wasi-sdk 20 pre-release for tests with threads (#2021)

`wasi-sdk-20` pre-release can be used to avoid building `wasi-libc` to enable threads.
It's not possible to use `wasi-sdk-20` pre-release on Ubuntu 20.04 because of
incompatibility with the glibc version:
```bash
/opt/wasi-sdk/bin/clang: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found
(required by /opt/wasi-sdk/bin/clang)
```

core/iwasm/libraries/lib-socket/test/build.sh

@@ -3,18 +3,17 @@
 # Copyright (C) 2023 Amazon.com Inc. or its affiliates. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-set -ueo pipefail
+set -eo pipefail
 CC="${CC:=/opt/wasi-sdk/bin/clang}"
 files=("tcp_udp.c" "nslookup.c")
-WASI_SYSROOT=${WASI_SYSROOT:=~/dev/wasi-libc/sysroot}
 
 for file in "${files[@]}"
 do
     echo $file
     $CC \
+        $WASI_SYSROOT_OPTION \
         --target=wasm32-wasi-threads \
         -I../inc \
-        --sysroot $WASI_SYSROOT \
         ../src/wasi/wasi_socket_ext.c -pthread -ftls-model=local-exec \
         -Wl,--allow-undefined \
         -Wl,--strip-all,--no-entry \