[DONT MERGE] Try enable O2 optimization #268

Job	Run time
host-win-msvc	2m 16s
host-win (x86_64)	1m 3s
host-arm (armv7, none, -O2, g++-10)	3m 10s
host-win (armv7)	58s
coding-style	21s
host-arm (armv7, none, -O2, clang++-11)	3m 13s
host-win (aarch64)	57s
host-x86 (x86_64, g++-10)	1m 25s
host-arm (aarch64, none, -O2, g++-10)	3m 12s
host-x86 (x86_64, clang++-11)	51s
host-arm (aarch64, none, -O2, clang++-11)	3m 12s
host-arm (aarch64, crypto+crc, -O2, g++-10)	3m 13s
host-arm (aarch64, crypto+crc, -O2, clang++-11)	3m 13s
host-arm (armv7, none, -mcpu=cortex-a32 -mfpu=neon-fp-armv8 -O2, g++-10)	3m 13s
host-arm (armv7, none, -mcpu=cortex-a32 -mfpu=neon-fp-armv8 -O2, clang++-11)	3m 14s
test-win-msvc	48s
	34m 19s

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