[llvm] [asan] Disable instrumentation for available_externally global with COFF (PR #81109)

[Fangrui Song via llvm-commits]

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+; This test checks that we are not instrumenting unnecessary globals
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MaskRay wrote:

I feel that we should better organize global variable tests by combining some into one file. They are currently scattered everywhere.

basic-msvc64.ll may be a better file for this test since basic.ll tests ELF available_externally.

https://github.com/llvm/llvm-project/pull/81109