Dependency workaround for FreeBSD/macOS systems

[Soneoylys]

Use ggrep as grep for BSD systems

This should resolve "command 'grep' function is incomplete, please install the full version first." as BSD systems use ggrep for GNU grep

Use md5 -r as md5sum for macOS systems

This should resolve conflicts while installing "md5sha1sum" and "coreutils" together via brew, as they both providing "md5sum" binary, none of them are required now

[Soneoylys]

should fix #140, tested on macOS Ventura & macOS Sonoma

[betaxab]

用变量不太好，要不然改成 function？