Android: ship stdlib grp module (Termux-style getgrent stub) — needed by proot-distro in Flet container apps #45

Request: build grp into the Android CPython (all ABIs, 3.12 + 3.13+), so import grp works in serious_python apps.

Context: I maintain a Flet Android app that wraps proot-distro (Linux containers on-device; related package request: flet-dev/flet#discussions/6979). proot-distro does import grp + import pwd unconditionally in proot_distro/helpers/rootfs.py and calls pwd.getpwuid(uid).pw_name / grp.getgrgid(g).gr_name when registering Android uid/gid entries into a container's /etc/passwd/group. On the Flet Android runtime (CPython 3.14) this fails: ModuleNotFoundError: No module named 'grp'.

Why it's missing (verified): CPython gates the module in configure.ac:

PY_STDLIB_MOD([grp], [], [test "$ac_cv_func_getgrent" = "yes" && { test "$ac_cv_func_getgrgid" = "yes" || test "$ac_cv_func_getgrgid_r" = "yes"; }])

Bionic only provides getgrent/setgrent/endgrent since API 26 (__INTRODUCED_IN(26) in grp.h; getgrgid_r has been there since API 24), while flet-dev/python-build targets api_level=24. On the 3.12 legacy flow the repo additionally forces it off via android/patches/grp.patch (Linux-android) py_cv_module_grp=n/a, inherited from Chaquopy: "we can't build the grp module, because getgrent and setgrent aren't available until API level 26"). On 3.13+ the exclusion happens naturally at the configure gate. Doc/library/grp.rst documents "not Android"; note pwd is not Android-excluded and appears to build fine.

Precedent — Termux ships grp: they hit the identical regression on their 3.12→3.13 upgrade (termux/termux-packages#28684, ModuleNotFoundError: No module named 'grp') and fixed it (PR termux/termux-packages#28768) by forcing ac_cv_func_getgrent=yes in packages/python/build.sh plus an NDK header patch (ndk-patches/30/grp.h.patch) that replaces the API-26 declarations with inline stubs:

static struct group* _Nullable getgrent(void) { return 0; }
static void setgrent(void) {}
static void endgrent(void) {}

Result: real getgrgid/getgrnam through Bionic (working since API 24), while getgrall() returns []. Chaquopy, Kivy's python-for-android, and Kodi instead treat grp as unsupported — Termux is the working counterexample.

Ask: adopt the Termux approach for the Android target: keep min-API 24, but ship grp with a getgrent-family fallback (build-time stub + ac_cv_func_getgrent=yes, or an equivalent in Modules/grpmodule.c) so getgrgid/getgrnam work and getgrall() degrades to [] on API 24–25. Ideally also drop/replace android/patches/grp.patch on the 3.12 flow accordingly.

I can test a pre-release build on-device immediately (import grp; grp.getgrgid(os.getgid()) under Android 16, arm64-v8a). Meanwhile my app ships a 20-line sys.modules shim for the two calls proot-distro makes, so this is a durability request, not a blocker for me.