[lld] [lld][AArch64] Add support for GCS (PR #90732)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,19 @@
+.section ".note.gnu.property", "a"
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MaskRay wrote:

`lld/test/ELF/Inputs/aarch64-func2-gcs.s` and `aarch64-func3-gcs.s` are extra files used only once.

We prefer split-file for newer tests (`# RUN: rm -rf %t && split-file %s %t && cd %t` in aarch64-feature-pauth.s)

https://github.com/llvm/llvm-project/pull/90732