[llvm] Recognize arm64 as target-aarch64 in lit

Recognize arm64 triples as AArch64 so we can XFAIL/skip tests using
target-aarch64.

Differential revision: https://reviews.llvm.org/D119169

llvm/utils/lit/lit/llvm/config.py

@@ -119,6 +119,8 @@ def __init__(self, lit_config, config):
                 features.add('target-x86_64')
             elif re.match(r'^aarch64.*', target_triple):
                 features.add('target-aarch64')
+            elif re.match(r'^arm64.*', target_triple):
+                features.add('target-aarch64')
             elif re.match(r'^arm.*', target_triple):
                 features.add('target-arm')