feat: use a submodule for ninja sources #591

Job	Run time
Lint	16s
Build source distribution	17s
Build x86_64 wheels on ubuntu-22.04	2m 15s
Build i686 wheels on ubuntu-22.04	2m 21s
Build aarch64 wheels on ubuntu-22.04	12m 49s
Build ppc64le wheels on ubuntu-22.04	11m 50s
Build s390x wheels on ubuntu-22.04	11m 51s
Build armv7l wheels on ubuntu-22.04	12m 50s
Build AMD64 wheels on windows-2019	2m 42s
Build ARM64 wheels on windows-2022	3m 58s
Build x86 wheels on windows-2019	2m 44s
Build universal2 wheels on macos-13	1m 53s
Test SDist with python 3.7	52s
Test SDist with python 3.12	49s
Check dist	1s
Upload to PyPI	1s
	1h 7m 29s

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