Log Message:
hgrep: update to 0.2.2.

Fix a build failure since new RC version of clap crate was released.
Fix a dynamic link error of pcre2 library by linking the library
statically. The error could happen when you installed Homebrew to
non-default location on macOS (#6).
Add --regex-size-limit option for built-in grep feature.
Add --dfa-size-limit option for built-in grep feature.
Use Rust compiler v1.57 to build binaries.