[lld] [lld][AArch64][ELF][PAC] Support AUTH relocations and AUTH ELF marking (PR #72714)

[Fangrui Song via llvm-commits]

================
@@ -0,0 +1,228 @@
+# REQUIRES: aarch64
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64 %p/Inputs/shared2.s -o main.so.o
----------------
MaskRay wrote:

When we use `main` in a test, we typically indicate that it belongs to the main executable.
A .o file linked into a DSO should not use a confusing name `main.so.o`. You can use a.o or b.o.

https://github.com/llvm/llvm-project/pull/72714