[llvm] [AArch64] Null check TargetStreamer before emitting .variant_pcs (PR #138924)

[Benjamin Maxwell via llvm-commits]

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@@ -2,6 +2,9 @@
 ; RUN: llc -mtriple=aarch64-linux-gnu -mattr=+sve -filetype=obj -o - %s \
 ; RUN:   | llvm-readobj --symbols - | FileCheck %s --check-prefix=CHECK-OBJ
 
+; Check we don't crash when using a Mach-O object format.
+; RUN: llc -mtriple=arm64-apple-macosx15.0.0 -mattr=+sve -filetype=obj -o /dev/null %s
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MacDue wrote:

Not sure I follow? All cases that cause a crash should never happen, but once fixed there should be a test to prevent a future regression. 

https://github.com/llvm/llvm-project/pull/138924