Remove `require_llvm` implementation

Remove `require_gcc` implementation

I was encountering some build issues on MicroOS and needed the actual exception message in order to pinpoint a workaround.

Co-authored-by: Mislav Marohnić <git@mislav.net>

This was only used in Ruby versions < 1.9.3, which are now EOL.

This also removes a 11-years old workaround for building Ruby 2.0 with clang.
06d7994b

This was used by Rubinius over the years to ensure that a correct llvm version was selected from the ones available on the system, but for recent Rubinius this function is a no-op, and since Rubinius isn't an actively maintained project anymore, I don't feel strongly for keeping ruby-build workarounds that only help ancient Rubinius versions.

Avoid test failure when stubbing FreeBSD environment

https://github.com/rbenv/ruby-build/actions/runs/5719870214/job/15517987944#step:4:18

Bump up OpenSSL versions

Bump up the latest versions of OpenSSL

* Use the new Oracle GraalVM distribution which uses the GFTC license as it is
  significantly faster than GraalVM CE and is free for development and production use.
* See https://medium.com/graalvm/whats-new-in-graalvm-languages-161527df3d76

Add JRuby 9.4.3.0

Added Ruby 3.3.0-preview1

* Use pkg info for readline/libedit prefix on FreeBSD instead of hardcoding it
* Use yaml and ffi installed via pkg on FreeBSD
* Remove check for FreeBSD version and allow all versions

Fix uploading SARIF reports from Differential Shellcheck

Mark EOL status to Ruby 2.6 and 2.7