On Windows, use c++20 mode as correctly needed for designated initial… #4099

Job	Run time
ClangTidy	1h 26m 25s
KytheVerification	25s
KytheXrefs	0s
MacOsBuild	43s
MacOsBuildDevTools	1m 34s
x86_64 test	3m 37s
Generate Build matrix	3s
arm64 test	4m 43s
PrepareVSPlugin	2m 19s
VerifyFormatting	1m 43s
x86_64 test-nortti	3m 44s
x86_64 test-c++20	3m 37s
WindowsBuild	2m 46s
x86_64 test-c++23	3m 36s
x86_64 smoke-test	15m 18s
arm64 smoke-test	14m 23s
x86_64 smoke-test-analyzer	17m 54s
arm64 smoke-test-analyzer	17m 39s
x86_64 asan	5m 11s
x86_64 asan-clang	4m 55s
x86_64 compile	3m 5s
arm64 compile	3m 57s
x86_64 compile-clang	2m 58s
arm64 compile-clang	3m 57s
x86_64 compile-static	2m 51s
arm64 compile-static	4m 10s
x86_64 compile-static-clang	3m 1s
arm64 compile-static-clang	3m 54s
x86_64 coverage	17m 24s
x86_64 clean	6m 59s
arm64 clean	6m 55s
Build ·${{ matrix.arch }}:${{ matrix.os }}:${{ matrix.ver }}${{ (((matrix.link == 'static') && ':static') \|\| '') }}	0s
Build and deploy GitHub pages	0s
📦 Release	0s
	4h 9m 46s

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