[clang] [clang] Add support for `[[msvc::forceinline]]` (PR #185282)

[Matt Arsenault via cfe-commits]

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+// RUN: %clang_cc1 -std=c++23 -emit-llvm %s -triple x86_64-pc-windows-msvc -o - | FileCheck %s
+
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arsenm wrote:

The point is to make sure it isn't artificially restricted to MSVC. You'll just need different check lines 

https://github.com/llvm/llvm-project/pull/185282