Build wasi-libc from source in WAMR CI (#2465)

We need to apply some bug fixes that were merged to wasi-libc because wasi-sdk-20
is about half a year old.

It is a temporary solution and the code will be removed when wasi-sdk 21 is released.

core/iwasm/libraries/lib-wasi-threads/test/build.sh

@@ -9,6 +9,30 @@ set -eo pipefail
 CC=${CC:=/opt/wasi-sdk/bin/clang}
 WAMR_DIR=../../../../..
 
+show_usage() {
+    echo "Usage: $0 [--sysroot PATH_TO_SYSROOT]"
+    echo "--sysroot PATH_TO_SYSROOT specify to build with custom sysroot for wasi-libc"
+}
+
+while [[ $# -gt 0 ]]; do
+    key="$1"
+    case $key in
+        --sysroot)
+            sysroot_path="$2"
+            shift
+            shift
+            ;;
+        --help)
+            show_usage
+            exit
+            ;;
+        *)
+            echo "Unknown option: $1"
+            exit 1
+            ;;
+    esac
+done
+
 # Stress tests names
 thread_start_file_exclusions=("spawn_stress_test.wasm" "linear_memory_size_update.wasm")
 
@@ -21,6 +45,14 @@ for test_c in *.c; do
         thread_start_file=$WAMR_DIR/samples/wasi-threads/wasm-apps/wasi_thread_start.S
     fi
 
+    if [[ -n "$sysroot_path" ]]; then 
+        if [ ! -d "$sysroot_path" ]; then 
+            echo "Directory $sysroot_path  doesn't exist. Aborting"
+            exit 1
+        fi
+        sysroot_command="--sysroot $sysroot_path"
+    fi
+    
     echo "Compiling $test_c to $test_wasm"
     $CC \
         -target wasm32-wasi-threads \
@@ -33,6 +65,7 @@ for test_c in *.c; do
         -Wl,--export=malloc \
         -Wl,--export=free \
         -I $WAMR_DIR/samples/wasi-threads/wasm-apps \
+        $sysroot_command \
         $thread_start_file \
         $test_c -o $test_wasm
 done