This involves:
* A small change to the Dockerfile, so that it checks the target
architecture and only installs gcc-multilib on x86_64.
* Updates to the GitHub Actions workflow build_aflplusplus_docker.yaml
to build for both linux/amd64 and linux/arm64.
These changes should allow Mac M1 users to get a working version of
AFL++ by doing "docker pull aflplusplus/aflplusplus".
* allow returning of str instead of CStr in rust custom mutator
* use OsStr instead of CStr for file paths
* fix cfg and compiler errors
* custom mutator default descriptions
* fix usage of afl_internal feature flag
* fix example mutator cfg
* fix lain mutator
* Revert "fix lain mutator"
This reverts commit adf7001808.
* actually fix lain mutator
* resolve question around utf-8 null bytes
* change from OsStr to Path to be even more ergonomic
* add rust custom mutator ci
* fix github action
* again
* separate compilation check
