Make ATfE buildable with cmake -DLLVM_TARGETS_TO_BUILD=ARM

[jiangyilism]

Problem or Opportunity
[A clear and concise description of what the problem or opportunity to improve is]

Building ATfE with cmake -DLLVM_TARGETS_TO_BUILD=ARM ... fails. Unless AArch64 is also appended to LLVM_TARGETS_TO_BUILD .

Requested Solution
Building ATfE with cmake -DLLVM_TARGETS_TO_BUILD=ARM ... .
Being able to opt out AArch64.

Additional context
branch arm-software, commit 0c47f0f
host: wsl-ubuntu