[lpyu001]

Emscripten 6.0.1 deprecated -sUSE_PTHREADS and -sMEMORY64 in favor of the standard -pthread and -m64 flags (emscripten-core/emscripten#27025). With the currently pinned Emscripten 6.0.10, both emit a -Wdeprecated warning at link time:

emcc: warning: USE_PTHREADS is deprecated (prefer the standard -pthread flag). [-Wdeprecated]
emcc: warning: MEMORY64 is deprecated (prefer the standard -m64 or --target=wasm64 flags). [-Wdeprecated]

This PR switches configure.ac to the standard flags:

• --enable-wasm-pthreads: -sUSE_PTHREADS → -pthread in LDFLAGS_NODIST. The existing -pthread in CFLAGS_NODIST is not passed to the link step, so the linker flag is still needed.
• wasm64-*-emscripten: -sMEMORY64=1 → -m64 in CFLAGS and LDFLAGS.
• Platforms/emscripten/README.md is updated to match.

I've also removed the Emscripten-specific NDOTDOTS = 48 workaround from test_glob_dotdot in Lib/test/test_pathlib/test_pathlib.py. Its comment says it can be removed once emscripten-core/emscripten#24591 is merged. That PR (don't return ELOOP on a path with many .. components) was merged in June 2025 and should be in 4.0.11 and later, well below the pinned 6.0.10. The test now uses NDOTDOTS = 50 on all platforms.

• Issue: Emscripten: Remove obsolete pthread_getattr_np workaround in ceval.c #160873

[lpyu001]

cc @hoodmane

[hoodmane]

Looks good to me.