Erlang/OTP 29.0.2 -> WebAssembly (Emscripten)

Compile the patched OTP tree in this repo into a wasm BEAM that boots and evaluates Erlang in the browser.

What is cross-compiled

Only erts (the BEAM emulator) -> bin/wasm32-unknown-emscripten/beam.{wasm,smp}. The .beam libraries (kernel/stdlib/compiler/…) are architecture-independent and taken from a native OTP install when the editor assembles the MEMFS image.

Threads and SharedArrayBuffer

OTP 29 has no --disable-smp: erts_start_schedulers() always creates OS threads. So the build uses Emscripten pthreads (Web Workers + SharedArrayBuffer), which requires the page to be cross-origin-isolated.

--disable-jit is used because wasm can't run the BeamAsm JIT.

erts patches

• erl_mmap.{c,h}: disable mremap (Emscripten/musl has none usable)
• sys.c: signal-dispatcher tolerates EAGAIN on the non-blocking pipe
• sys_drivers.c: forker_start is a no-op (removed OS process ports)