Follow-up to #83. Five small fixes I caught while reviewing:
- build_lib: spell out the stdlib-only invariant in the module docstring.
build-version.py is called from app/build.gradle.kts on every Gradle
build, so adding pip/uv deps here would break the APK build.
- build_lib: drop unused get_python_exe() (no callers anywhere).
- build_lib: add version_sort_key() and use it in zygisk and kmod for
NDK / clang auto-detection. The previous lexicographic sorted() picked
the wrong directory when major versions span different digit widths
(e.g. 100.0.0 < 25.0.1, clang-r9 sorting after clang-r498344b).
zygisk/build-zip.sh used `sort -V` before the python port, so this is
a regression fix; kmod is a new safety net (DDK containers ship one
clang today, but auto-detect should still be correct).
- kmod/build-zip.py: drop the manual mtime check before `make strip`.
The check only watched vpnhide_kmod.c, so edits to the Makefile,
kernel headers, or .config wouldn't trigger a rebuild. Let make's own
dependency tracking decide.
- build_lib: minor cleanup — hoist `import subprocess` to the top of
the module instead of importing it inside get_build_version().
