add a new min_dio_alignment helper

add a new min_dio_alignment helper

Add a new C program to find the minimum direct I/O alignment.  This
uses the statx stx_dio_offset_align field if provided, then falls
back to the BLKSSZGET ioctl for block backed file systems and finally
the page size.  It is intended as a more capable replacement for the
_min_dio_alignment bash helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>