Build boost library to emscripten

[juanlanuzag]

Hello, I am trying to port an existing program to wasm and this program uses boost program options.
I downloaded and boostrapped boost and I'm running
`
./b2 toolset=emscripten link=static threading=multi --with-program_options

I am getting the following warning for multiple files

emcc: warning: .bc output file suffix used without -flto or -emit-llvm.  Consider using .o extension since emcc will output an object file, not a bitcode file [-Wemcc]
emscripten.compile.c++ bin.v2/libs/program_options/build/emscripten-3.1.69/release/link-static/threading-multi/visibility-hidden/split.bc

and the following error

emscripten.archive bin.v2/libs/program_options/build/emscripten-3.1.69/release/link-static/threading-multi/visibility-hidden/libboost_program_options.bc
bin.v2/libs/program_options/build/emscripten-3.1.69/release/link-static/threading-multi/visibility-hidden/cmdline.bc:1:2: error: expected top-level entity
    1 | <U+0000>asm<U+0001><U+0000><U+0000><U+0000><U+0001>ƀ<80><80><U+0000><U+000B>`

Any idea what is this issue? Is my approach correct?

Version of emscripten/emsdk:

emcc -v
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.69 (c55ff404dbe1eb9f263c48b584d5ba627224763a)
clang version 20.0.0git (https:/github.com/llvm/llvm-project 50866e84d1da8462aeb96607bf6d9e5bbd5869c5)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /home/myuser/emsdk/upstream/bin

[sbc100]

Looks like the build system needs to be updated to switch from .bc to .o for the object file extension.