The files in /build were generated using the steps proposed by wide-video / piper-wasm.
As of JUN 2024:
# Docker (optional)
docker run -it -v $(pwd):/wasm -w /wasm debian:11.3
apt-get update
apt-get install --yes --no-install-recommends build-essential cmake ca-certificates curl pkg-config git python3 autogen automake autoconf libtool
# Emscripten
git clone --depth 1 https://github.com/emscripten-core/emsdk.git /wasm/modules/emsdk
cd /wasm/modules/emsdk
./emsdk install 3.1.47
./emsdk activate 3.1.47
source ./emsdk_env.sh
TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
sed -i -E 's/int\s+(iswalnum|iswalpha|iswblank|iswcntrl|iswgraph|iswlower|iswprint|iswpunct|iswspace|iswupper|iswxdigit)\(wint_t\)/\/\/\0/g' ./upstream/emscripten/cache/sysroot/include/wchar.h
# espeak-ng
git clone --depth 1 https://github.com/rhasspy/espeak-ng.git /wasm/modules/espeak-ng
cd /wasm/modules/espeak-ng
./autogen.sh
./configure
make
# piper-phonemize
git clone --depth 1 https://github.com/wide-video/piper-phonemize.git /wasm/modules/piper-phonemize
cd /wasm/modules/piper-phonemize
emmake cmake -Bbuild -DCMAKE_INSTALL_PREFIX=install -DCMAKE_TOOLCHAIN_FILE=$TOOLCHAIN_FILE -DBUILD_TESTING=OFF -G "Unix Makefiles" -DCMAKE_CXX_FLAGS="-O3 -s INVOKE_RUN=0 -s MODULARIZE=1 -s EXPORT_NAME='createPiperPhonemize' -s EXPORTED_FUNCTIONS='[_main]' -s EXPORTED_RUNTIME_METHODS='[callMain, FS]' --preload-file /wasm/modules/espeak-ng/espeak-ng-data@/espeak-ng-data"
emmake cmake --build build --config Release # fails on "Compile intonations / Permission denied", continue with next steps
sed -i 's+$(MAKE) $(MAKESILENT) -f CMakeFiles/data.dir/build.make CMakeFiles/data.dir/build+#\0+g' /wasm/modules/piper-phonemize/build/e/src/espeak_ng_external-build/CMakeFiles/Makefile2
sed -i 's/using namespace std/\/\/\0/g' /wasm/modules/piper-phonemize/build/e/src/espeak_ng_external/src/speechPlayer/src/speechWaveGenerator.cpp
emmake cmake --build build --config Release