🚨 Remove GNU extension #1644

Job	Run time
quality_checks_pass	1m 16s
sanitize (undefined, clang)	3m 52s
sanitize (undefined, gcc)	2m 52s
build_and_test_22 (clang, 14, 20, libc++, Debug)	2m 47s
valgrind	3m 10s
sanitize (address, clang)	3m 29s
build_and_test_22 (clang, 15, 20, libstdc++, Debug)	2m 45s
build_and_test_24 (clang, 16, 20, libstdc++, Debug)	3m 22s
sanitize (address, gcc)	3m 6s
build_and_test_22 (clang, 15, 20, libc++, Debug)	3m 12s
build_and_test_24 (clang, 16, 20, libc++, Debug)	3m 33s
sanitize (thread, clang)	3m 41s
sanitize (thread, gcc)	2m 49s
build_and_test_24 (clang, 17, 20, libstdc++, Debug)	3m 16s
build_and_test_24 (clang, 17, 20, libc++, Debug)	3m 59s
build_and_test_24 (clang, 18, 20, libstdc++, Debug)	4m 5s
build_and_test_24 (clang, 18, 20, libc++, Debug)	4m 1s
build_and_test_24 (gcc, 12, 20, libstdc++, Debug)	2m 41s
build_and_test_24 (gcc, 13, 20, libstdc++, Debug)	3m 2s
merge_ok	3s
	1h 1m 1s

Provide feedback