[llvm] [AArch64][SME] Use reportFatalUsageError rather than assert (NFC) (PR #145491)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,7 @@
+; RUN: not llc -mtriple aarch64-none-linux-gnu %s 2>&1 | FileCheck %s
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arsenm wrote:

Should use -filetype=null 

https://github.com/llvm/llvm-project/pull/145491