Add a conditional compilation directive to be compatible with C++26 (… #845

Job	Run time
ubu-24 \| g++-14 \| c++2b \| libstdc++ \| ubuntu-24.04	6m 18s
ubu-24 \| g++-13 \| c++2b \| libstdc++ \| ubuntu-24.04	5m 29s
ubu-20 \| g++-10 \| c++20 \| libstdc++ \| ubuntu-20.04	5m 18s
ubu-24 \| clang++-18 \| c++20 \| libstdc++ \| ubuntu-24.04	7m 2s
ubu-24 \| clang++-18 \| c++23 \| libc++-18-dev \| ubuntu-24.04	7m 9s
ubu-22 \| clang++-15 \| c++20 \| libstdc++ \| ubuntu-22.04	5m 31s
ubu-22 \| clang++-15 \| c++20 \| libc++-15-dev \| ubuntu-22.04	5m 44s
ubu-20 \| clang++-12 \| c++20 \| libstdc++ \| ubuntu-20.04	5m 7s
mac-14 \| clang++ \| c++2b \| default \| macos-14	2m 24s
mac-13 \| clang++ \| c++2b \| default \| macos-13	5m 40s
mac-13 \| clang++-15 \| c++2b \| default \| macos-13	8m 33s
win-22 \| cl.exe \| c++latest \| default \| windows-2022	4m 16s
win-22 \| cl.exe \| c++20 \| default \| windows-2022	4m 10s
aggregate-results	6s
	1h 12m 47s

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