specify runner os versions #889

Job	Run time
build-linux (debug, static_lib)	27s
build-darwin (debug, static_lib, x64)	36s
build-linux (debug, shared_lib)	29s
cancel-old-build	2s
build-darwin (debug, static_lib, arm64)	38s
build-win32 (debug, static_lib)	1m 1s
build-linux (debug, cmd)	35s
build-darwin (debug, shared_lib, x64)	31s
build-win32 (debug, shared_lib)	1m 6s
build-linux (release, static_lib)	1m 23s
build-darwin (debug, shared_lib, arm64)	33s
build-win32 (debug, cmd)	1m 16s
test-darwin (debug, arm64)	48s
build-linux (release, shared_lib)	52s
build-darwin (debug, cmd, x64)	41s
build-win32 (release, static_lib)	1m 47s
test-darwin (debug, x64)	49s
build-linux (release, cmd)	48s
build-darwin (debug, cmd, arm64)	44s
build-win32 (release, shared_lib)	1m 46s
test-darwin (release, arm64)	56s
build-darwin (release, static_lib, x64)	1m 3s
build-win32 (release, cmd)	1m 36s
test-darwin (release, x64)	1m 15s
build-darwin (release, static_lib, arm64)	1m 3s
test-linux (debug)	44s
build-darwin (release, shared_lib, x64)	53s
test-linux (release)	49s
build-darwin (release, shared_lib, arm64)	57s
test-win32 (debug)	46s
build-darwin (release, cmd, x64)	1m 18s
test-win32 (release)	3m 17s
build-darwin (release, cmd, arm64)	49s
dist-linux	6s
dist-win32	20s
dist-darwin (x64)	22s
dist-darwin (arm64)	27s
	33m 33s

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