On Windows, use c++20 mode as correctly needed for designated initial… #4098

Job	Run time
KytheVerification	43s
ClangTidy	1h 24m 21s
MacOsBuildDevTools	1m 36s
Generate Build matrix	2s
x86_64 test	3m 18s
VerifyFormatting	1m 44s
arm64 test	5m 4s
KytheXrefs	0s
x86_64 test-nortti	3m 14s
x86_64 test-c++20	3m 15s
MacOsBuild	36s
x86_64 test-c++23	3m 36s
PrepareVSPlugin	2m 12s
x86_64 smoke-test	11m 35s
WindowsBuild	37m 8s
arm64 smoke-test	14m 45s
x86_64 smoke-test-analyzer	14m 47s
arm64 smoke-test-analyzer	17m 27s
x86_64 asan	5m 10s
x86_64 asan-clang	5m 7s
x86_64 compile	2m 53s
arm64 compile	3m 56s
x86_64 compile-clang	2m 53s
arm64 compile-clang	3m 55s
x86_64 compile-static	2m 56s
arm64 compile-static	3m 52s
x86_64 compile-static-clang	2m 35s
arm64 compile-static-clang	3m 55s
x86_64 coverage	14m 16s
x86_64 clean	7m 3s
arm64 clean	7m 8s
Build ·${{ matrix.arch }}:${{ matrix.os }}:${{ matrix.ver }}${{ (((matrix.link == 'static') && ':static') \|\| '') }}	0s
Build and deploy GitHub pages	0s
📦 Release	0s
	4h 31m 2s

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