fix compatible issue with gcc-9 (#72) #467

Job	Run time
arenastring-gcc-stdlibc++-default	1m 38s
aarch64	1m 46s
arenastring-gcc-stdlibc++-half	1m 34s
arenastring-gcc-stdlibc++-full	1m 42s
cmake	1m 40s
arenastring-clang-stdlibc++-default	1m 33s
basic-gcc-dbg-c++20-stdlibc++-asan	1m 34s
arenastring-clang-libc++-default	1m 43s
compatible-gcc-9	9m 18s
basic-gcc-dbg-c++20-stdlibc++-tsan	1m 33s
basic-gcc-dbg-c++14-stdlibc++-asan	1m 23s
coverage	1m 55s
basic-gcc-opt-c++20-stdlibc++-asan	1m 52s
cpp14-coroutine	1m 16s
basic-gcc-opt-c++20-stdlibc++-tsan	1m 38s
basic-gcc-opt-c++14-stdlibc++-asan	1m 27s
workspace	58s
basic-clang-dbg-c++20-stdlibc++-asan	1m 51s
basic-clang-dbg-c++20-stdlibc++-tsan	1m 48s
basic-clang-dbg-c++20-libc++-asan	2m 6s
basic-clang-dbg-c++20-libc++-tsan	1m 59s
basic-clang-dbg-c++14-stdlibc++-asan	1m 27s
basic-clang-dbg-c++14-libc++-asan	2m 17s
basic-clang-opt-c++20-stdlibc++-asan	1m 56s
basic-clang-opt-c++20-stdlibc++-tsan	1m 52s
basic-clang-opt-c++20-libc++-asan	1m 59s
basic-clang-opt-c++20-libc++-tsan	1m 56s
basic-clang-opt-c++14-stdlibc++-asan	1m 53s
basic-clang-opt-c++14-libc++-asan	1m 40s
	57m 14s

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