[lld] [LLD][COFF] Add basic ARM64X dynamic relocations support (PR #118035)

[Martin Storsjö via llvm-commits]

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+// REQUIRES: aarch64
+// RUN: split-file %s %t.dir && cd %t.dir
+
+// RUN: llvm-mc -filetype=obj -triple=aarch64-windows test.s -o test.obj
+// RUN: llvm-mc -filetype=obj -triple=aarch64-windows loadconfig.s -o loadconfig.obj
+// RUN: llvm-mc -filetype=obj -triple=aarch64-windows loadconfig-short.s -o loadconfig-short.obj
+
+// RUN: lld-link -machine:arm64x -out:out.dll -dll -noentry loadconfig.obj test.obj
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mstorsjo wrote:

So we're testing writing an arm64x image, but where we only have plain aarch64 chunks? And if changing to the arm64ec form at runtime, it changes the machine field and clears the load config, but nothing else?

https://github.com/llvm/llvm-project/pull/118035