AArch64: Use reportFatalUsageError for unsupported calling conv#144840

arsenm merged 2 commits intomainllvm/llvm-project:mainfrom

users/arsenm/aarch64/reportFatalUsageError-unsupported-calling-conventionllvm/llvm-project:users/arsenm/aarch64/reportFatalUsageError-unsupported-calling-conventionCopy head branch name to clipboard