Add Emscripten builds to releases

[bmaranville]

Is your feature request related to a problem? Please describe.
I would like to have Emscripten added to the list of architectures for which the library is pre-built and distributed with releases, such as osx12 and ubuntu-2204

Describe the solution you'd like
If the hdf5 library was built with emscripten at every release and the binary package attached as a release artifact

Describe alternatives you've considered
I am currently doing this myself for a selected set of HDF5 versions here: https://github.com/usnistgov/libhdf5-wasm - I would like it if this architecture was officially supported and I didn't build it myself. (I'm not particularly good at CMake)

Additional context
I recently changed my build process to use the provided CPack configuration from HDF5, and it seems to work well. I believe this could be built almost as easily as the packages for the other architectures.

[derobins]

This would be interesting, but requires more discussion. Moving to the 'discussion' section.

[bmaranville]

This seems to be pretty straightforward now - if I check out hdf5 v1.14.6 from github, I can build a usable distribution package for Emscripten with these additional settings:

# CMakeWASM.cmake
# (additional settings for building with Emscripten)
set(CMAKE_EXE_LINKER_FLAGS_INIT "-sNODERAWFS=1 -sFORCE_FILESYSTEM=1 -sSINGLE_FILE=1" CACHE INTERNAL "")
set(HDF5_BUILD_JAVA OFF CACHE STRING "turn off building java for WASM target" FORCE)
set(HDF5_BUILD_FORTRAN OFF CACHE STRING "turn off building fortran for WASM target" FORCE)
option(BUILD_TESTING "build testing" OFF)
option(BUILD_SHARED_LIBS "Build shared libs" OFF)
option(HDF5_BUILD_EXAMPLES "Build Examples" OFF)
set(HDF5_PACKAGE_EXTLIBS ON CACHE BOOL "" FORCE)
set (HDF5_ALLOW_EXTERNAL_SUPPORT "GIT" CACHE STRING "Allow External Library Building (NO GIT TGZ)" FORCE)

option(HDF5_ENABLE_Z_LIB_SUPPORT "Enable ZLIB" ON)
option (ZLIB_USE_LOCALCONTENT "Use local file for ZLIB FetchContent" OFF)
set (ZLIB_GIT_URL "https://github.com/madler/zlib.git" CACHE STRING "Use ZLIB from  GitHub repository" FORCE)
set (ZLIB_GIT_BRANCH "v1.3.1" CACHE STRING "" FORCE)

option(HDF5_ENABLE_SZIP_SUPPORT "Enable SZIP" ON)
option (LIBAEC_USE_LOCALCONTENT "Use local file for LIBAEC FetchContent" OFF)
set (LIBAEC_GIT_URL "https://github.com/MathisRosenhauer/libaec.git" CACHE STRING "Use LIBAEC from  GitHub repository" FORCE)
set (LIBAEC_GIT_BRANCH "v1.1.3" CACHE STRING "" FORCE)

(using Emscripten v3.1.68, cmake v3.31.6, ninja v1.12.1)

emcmake cmake -C config/cmake/cacheinit.cmake -C CMakeWASM.cmake -G Ninja -S . -B build_wasm
cmake --build build_wasm --target package

(results in HDF5-1.14.6-Emscripten.tar.gz among others)

[bmaranville]

With the caveat that the source still has to be patched as here: https://github.com/usnistgov/libhdf5-wasm/blob/main/patches/1.14.6/FE_INVALID.patch since that change was merged I think, but not backported to any of the 1.14.x versions.