Re: [Libguestfs] [PATCH commit] options: Compile blocksize code conditionally.

Since the blocksize option was added since the minimum version of libguestfs for virt-v2v, we need to make it conditional so that virt-v2v can still be compiled with the older libguestfs. This commit does the minimum fix to make it build. It doesn't conditionalize the --blocksize option altogether. However I believe, at least for virt-v2v, that is OK since the --blocksize option is not used there.