[cpp] Add OpenBSD to CMakeLists.txt #1048

Job	Run time
cpp-lib-build (macos-11, clang, ON)	10m 8s
build (macos-11, tool)	2m 14s
cpp-lib-build (macos-11, clang, OFF)	9m 20s
build (macos-11, cpp)	41m 48s
cpp-lib-build (macos-11, gcc, ON)	14m 45s
build (macos-11, csharp)	13m 38s
cpp-lib-build (macos-11, gcc, OFF)	9m 56s
build (macos-11, dart)	7m 57s
cpp-lib-build (ubuntu-20.04, clang, ON)	4m 47s
build (macos-11, go)	5m 25s
cpp-lib-build (ubuntu-20.04, clang, OFF)	4m 37s
build (macos-11, java)	2m 10s
cpp-lib-build (ubuntu-20.04, gcc, ON)	3m 34s
build (macos-11, javascript)	5m 53s
cpp-lib-build (ubuntu-20.04, gcc, OFF)	3m 29s
build (macos-11, typescript)	28m 18s
cpp-lib-build (windows-2022, clang, ON)	6m 16s
build (macos-11, php)	23s
cpp-lib-build (windows-2022, clang, OFF)	5m 35s
build (macos-11, python3)	5m 31s
cpp-lib-build (windows-2022, cl)	4m 48s
build (ubuntu-20.04, tool)	1m 6s
build (ubuntu-20.04, cpp)	17m 30s
build (ubuntu-20.04, csharp)	5m 10s
build (ubuntu-20.04, dart)	3m 42s
build (ubuntu-20.04, go)	2m 23s
build (ubuntu-20.04, java)	1m 20s
build (ubuntu-20.04, javascript)	1m 24s
build (ubuntu-20.04, typescript)	10m 11s
build (ubuntu-20.04, php)	1m 18s
build (ubuntu-20.04, python3)	1m 6s
build (windows-2022, tool)	1m 33s
build (windows-2022, cpp)	21m 41s
build (windows-2022, csharp)	7m 24s
build (windows-2022, dart)	4m 21s
build (windows-2022, go)	6m 14s
build (windows-2022, java)	2m 21s
build (windows-2022, javascript)	2m 43s
build (windows-2022, typescript)	21m 20s
build (windows-2022, php)	2m 24s
build (windows-2022, python3)	1m 45s
	5h 7m 28s

Provide feedback