CI: install system packages for sdist job #597

Job	Run time
coverage	7m 44s
test-cxx (ubuntu-20.04, g++-9, enabled)	47s
test-cxx (ubuntu-22.04, g++-12, enabled)	1m 41s
test-cxx (ubuntu-20.04, clang++-10, enabled)	1m 15s
test-cxx (ubuntu-22.04, clang++-14, enabled)	41s
test-cxx (macos-12, clang++, disabled)	8m 1s
test-python (ubuntu-20.04, gcc-9, g++-9, 3.8, enabled)	5m 44s
test-python (ubuntu-22.04, gcc-12, g++-12, 3.12.0-rc.1, enabled)	4m 48s
test-python (ubuntu-20.04, clang-10, clang++-10, 3.12.0-rc.1, enabled)	5m 19s
test-python (ubuntu-22.04, clang-14, clang++-14, 3.12.0-rc.1, enabled)	5m 39s
test-python (macos-12, clang, clang++, 3.12.0-rc.1, disabled)	12m 43s
cibuildwheel	4m 34s
sdist	45s
	59m 41s

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