On Windows, use c++20 mode as correctly needed for designated initial… #4096

Job	Run time
ClangTidy	1h 26m 50s
KytheVerification	37s
KytheXrefs	0s
MacOsBuild	34s
x86_64 test	3m 43s
MacOsBuildDevTools	1m 23s
arm64 test	5m 12s
Generate Build matrix	3s
PrepareVSPlugin	2m 0s
x86_64 test-nortti	4m 3s
VerifyFormatting	1m 42s
x86_64 test-c++20	3m 35s
WindowsBuild	2m 16s
x86_64 test-c++23	3m 45s
x86_64 smoke-test	14m 10s
arm64 smoke-test	14m 37s
x86_64 smoke-test-analyzer	18m 39s
arm64 smoke-test-analyzer	18m 3s
x86_64 asan	5m 39s
x86_64 asan-clang	4m 45s
x86_64 compile	2m 57s
arm64 compile	4m 9s
x86_64 compile-clang	2m 57s
arm64 compile-clang	4m 12s
x86_64 compile-static	3m 18s
arm64 compile-static	3m 51s
x86_64 compile-static-clang	2m 58s
arm64 compile-static-clang	4m 4s
x86_64 coverage	18m 6s
x86_64 clean	7m 7s
arm64 clean	6m 49s
Build ·${{ matrix.arch }}:${{ matrix.os }}:${{ matrix.ver }}${{ (((matrix.link == 'static') && ':static') \|\| '') }}	0s
Build and deploy GitHub pages	0s
📦 Release	0s
	4h 12m 4s

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