Align the block_size to a power of 2 on Windows. #3

Job	Run time
nmake workflow	9m 50s
autoconf workflow using Default	3m 23s
autoconf workflow using LLVM	2m 59s
autoconf workflow using Debug	5m 27s
autoconf workflow using Profiling	12m 52s
autoconf workflow using Address Sanitition	5m 40s
autoconf workflow using Thread Sanitition	2m 21s
autoconf workflow using No Optimization	3m 29s
autoconf workflow using Native Optimization	3m 14s
autoconf workflow using Static Library	3m 24s
autoconf workflow using zlib	3m 25s
autoconf workflow using zstd	3m 28s
autoconf workflow using lz4	3m 7s
autoconf workflow using lzma	3m 8s
autoconf workflow using most features	3m 7s
	1h 8m 54s

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