Function bootstrap::llvm::is_ci_llvm_available

pub(crate) fn is_ci_llvm_available(config: &Config, asserts: bool) -> bool

Returns whether the CI-found LLVM is currently usable.

This checks both the build triple platform to confirm we’re usable at all, and then verifies if the current HEAD matches the detected LLVM SHA head, in which case LLVM is indicated as not available.