matrix in matrix? #300

Job	Run time
build-and-test (14, ubuntu-latest, amd64, false)	1m 31s
build-and-test (14, macos-12, amd64, false)	2m 9s
build-and-test (14, windows-latest, amd64, false)	2m 5s
build-and-test (16, ubuntu-latest, amd64, false)	1m 44s
build-and-test (16, macos-12, amd64, false)	2m 10s
build-and-test (16, windows-latest, amd64, false)	2m 4s
build-and-test (18, ubuntu-latest, amd64, false)	1m 38s
build-and-test (18, macos-12, amd64, false)	2m 11s
build-and-test (18, windows-latest, amd64, false)	2m 5s
build-and-test (19, ubuntu-latest, amd64, false)	1m 36s
build-and-test (19, macos-12, amd64, false)	2m 10s
build-and-test (19, windows-latest, amd64, false)	2m 5s
build-and-test (20, ubuntu-latest, amd64, false)	1m 27s
build-and-test (20, macos-12, amd64, false)	2m 10s
build-and-test (20, windows-latest, amd64, false)	2m 5s
build-and-test (macos-14, arm64, 14, 16, 18, 19, 20)	1s
build-and-test (ubuntu-latest, arm64, true, 14, 16, 18, 19, 20)	1m 37s
build-and-test (ubuntu-latest, amd64, true, 14, 16, 18, 19, 20)	1m 32s
	32m 20s

Provide feedback