[clang] [llvm] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #77424)

[Yingwei Zheng via cfe-commits]

================
@@ -0,0 +1,11 @@
+# RUN: not llvm-mc -triple riscv32 -mattr=+experimental-zaamo < %s 2>&1 | FileCheck %s
----------------
dtcxzyw wrote:

Can we split `rv32a-invalid.s` into two files? I think it is better than duplicating tests for new extensions.


https://github.com/llvm/llvm-project/pull/77424