Rollup merge of #105026 - oToToT:aarch64-v8a, r=davidtwco

v8a as default aarch64 target

After https://github.com/llvm/llvm-project/commit/8689f5e landed, LLVM takes the intersection of v8a and v8r as default. This commit brings back v8a support by explicitly specifying v8a in the feature list.

This should solve #97724.

p.s. a bit more context can also be found in https://github.com/llvm/llvm-project/issues/57904#issuecomment-1329555590.

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -494,6 +494,11 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
         .flatten();
     features.extend(feats);
 
+    // FIXME: Move v8a to target definition list when earliest supported LLVM is 14.
+    if get_version() >= (14, 0, 0) && sess.target.arch == "aarch64" {
+        features.push("+v8a".into());
+    }
+
     if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
         sess.emit_err(TargetFeatureDisableOrEnable {
             features: f,