Simplify for modular building. #1439

Job	Run time
b2-windows (windows-2019)	25m 34s
cmake-install-windows (windows-2019)	11m 37s
cmake-install-posix (ubuntu-20.04)	6m 33s
b2-windows (windows-2022)	25m 43s
cmake-install-windows (windows-2022)	9m 30s
b2-posix (ubuntu-20.04)	15m 7s
cmake-install-posix (ubuntu-22.04)	4m 18s
b2-posix (ubuntu-22.04)	11m 16s
cmake-install-posix (macos-11)	9m 41s
b2-posix (macos-11)	21m 52s
cmake-test-posix (ubuntu-latest)	57m 22s
cmake-install-posix (macos-12)	15m 47s
cmake-test-posix-quick (ubuntu-20.04)	3m 48s
b2-posix (macos-12)	16m 44s
cmake-install-posix (macos-13)	8m 55s
cmake-test-posix-quick (ubuntu-22.04)	2m 19s
b2-posix (macos-13)	17m 13s
cmake-test-posix-quick (macos-11)	6m 33s
cmake-test-windows-quick (windows-2019)	10m 29s
cmake-test-posix-quick (macos-12)	7m 44s
cmake-test-windows-quick (windows-2022)	5m 38s
cmake-test-posix-quick (macos-13)	5m 22s
	4h 59m 5s

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