bench.c: ignore directories from a file list for benchmark
bench.c: ignore directories from a file list for benchmark

inikep/zstd,Majlen/zstd,ds77/zstd,inikep/zstd,Cyan4973/zstd,Cyan4973/zstd,ds77/zstd,inikep/zstd,ds77/zstd,Majlen/zstd,Cyan4973/zstd,inikep/zstd,Majlen/zstd,ds77/zstd,Majlen/zstd,Cyan4973/zstd,Cyan4973/zstd