Add WASM build script for wasm32-wasip2 target

Add resources/build_wasm.sh that cross-compiles the package as a WASM
wheel targeting wasm32-wasip2. The script sets up a host venv, configures
the WASI SDK toolchain (clang, ar, linker flags), and uses `python -m
build` to produce the wheel, then unpacks it into build/.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kesmit13

resources/build_wasm.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+
+set -eou pipefail
+
+# CPYTHON_ROOT must contain a build of cpython for wasm32-wasip2
+
+TARGET="wasm32-wasip2"
+CROSS_BUILD="${CPYTHON_ROOT}/cross-build/${TARGET}"
+WASI_SDK_PATH=${WASI_SDK_PATH:-/opt/wasi-sdk}
+PYTHON_VERSION=$(grep '^VERSION=' "${CROSS_BUILD}/Makefile" | sed 's/VERSION=[[:space:]]*//')
+
+if [ ! -e wasm_venv ]; then
+  uv venv --python ${PYTHON_VERSION} wasm_venv
+fi
+
+. wasm_venv/bin/activate
+
+HOST_PYTHON=$(which python3)
+
+uv pip install build wheel cython setuptools
+
+ARCH_TRIPLET=_wasi_wasm32-wasi
+
+export CC="${WASI_SDK_PATH}/bin/clang"
+export CXX="${WASI_SDK_PATH}/bin/clang++"
+
+export PYTHONPATH="${CROSS_BUILD}/build/lib.wasi-wasm32-${PYTHON_VERSION}"
+
+export CFLAGS="--target=${TARGET} -fPIC -I${CROSS_BUILD}/install/include/python${PYTHON_VERSION} -D__EMSCRIPTEN__=1"
+export CXXFLAGS="--target=${TARGET} -fPIC -I${CROSS_BUILD}/install/include/python${PYTHON_VERSION}"
+export LDSHARED=${CC}
+export AR="${WASI_SDK_PATH}/bin/ar"
+export RANLIB=true
+export LDFLAGS="--target=${TARGET} -shared -Wl,--allow-undefined"
+export _PYTHON_SYSCONFIGDATA_NAME=_sysconfigdata__wasi_wasm32-wasi
+export _PYTHON_HOST_PLATFORM=wasm32-wasi
+
+python3 -m build -n -w
+wheel unpack --dest build dist/*.whl
+
+rm -rf ./wasm_venv