Parallelize deepfreeze.py

Feature or enhancement

I propose to parallelize deepfreezing to speed up compile time for core devs.

Pitch

deepfreezing / deepfreeze.py is a choke point for building CPython. Deepfreezing happens very late in the build process and takes considerable amount of time, especially for pydebug builds. Deepfreezing is a single process and does not benefit from multiple cores. Every build that touches a core file will result in re-freezing. On my system and with ccache populates, make spends between 60 to 75% time just in deepfreeze.py for debug builds. For regular builds it's about 25-30% of total build time.

$ ./configure -C --with-pydebug
$ make clean
$ time make

real    0m9,339s
user    0m13,630s
sys     0m2,657s

$ rm Python/deepfreeze/deepfreeze.c
$ time make Python/deepfreeze/deepfreeze.c

real    0m7,267s
user    0m7,033s
sys     0m0,204s

The process can be parallelized. One possible solution is to split the work. For each input module create a make rule that outputs an inc file, e.g. Python/deepfreeze/"importlib._bootstrap.inc. An another rules creates deepfreeze.c with #include "importlib._bootstrap.inc, ... This keeps all code in one object file.

Bắt đầu với Python/deepfreeze/deepfreeze.py và các lệnh build được nêu trong issue, sau đó truy vết cách Python/deepfreeze/deepfreeze.c được tạo. Đánh giá các đầu ra .inc theo từng đầu vào được đề xuất và các quy tắc build. Hoàn thành khi deepfreezing có thể sử dụng nhiều core, đồng thời tạo ra đầu ra deepfreeze.c bắt buộc và giữ nguyên quy trình build hiện tại.