CI: build wamr-wasi-extensions (#4394)

* wamr-wasi-extensions: separate test scripts
also, allow to specify the prefix directory.
for the convenience of the CI.

* CI: build wamr-wasi-extensions
fragments are copied from compilation_on_macos.yml.
(thus intel copyright notice)

wamr-wasi-extensions/build_libs.sh

@@ -0,0 +1,15 @@
+#! /bin/sh
+
+# Copyright (C) 2025 Midokura Japan KK.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+set -e
+
+PREFIX=${1:-/tmp/wamr}
+WASI_SDK=${WASI_SDK:-/opt/wasi-sdk}
+
+cmake -B build-lib \
+-DCMAKE_TOOLCHAIN_FILE=${WASI_SDK}/share/cmake/wasi-sdk.cmake \
+-DCMAKE_INSTALL_PREFIX=${PREFIX} \
+.
+cmake --build build-lib -t install