RVM warns users about building under clang too broadly

[JasonLunn]

Description

When installing Ruby from source, RVM emits warnings about building under clang.

Steps to reproduce

1. install fresh RVM
2. rvm install ruby-head

Reproduces using rvm from master.

Expected behavior

No warning is emitted. Building Ruby under clang is fully supported.

Actual behavior

Ruby 'ruby-3.3.0' was built using clang - but it's not (fully) supported, expect errors is observed first (while RVM is building ruby-3.3) and then later Ruby 'ruby-head' was built using clang - but it's not (fully) supported, expect errors. while it is building ruby at head (currently 3.4.0dev).

Environment info

Debian-based docker container based on gcr.io/clang-docker-builder/clang-debian10@sha256:6ec05ec712da7e31c2b74b24d403301a399adae7696c86738530d375ea2224eb