[clang-tools-extra] [clang-tidy] Teach `cppcoreguidelines-interfaces-global-init` about `constinit` (PR #148334)

[Baranov Victor via cfe-commits]

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@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s cppcoreguidelines-interfaces-global-init %t
+// RUN: %check_clang_tidy -std=c++20 %s cppcoreguidelines-interfaces-global-init %t
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vbvictor wrote:

We shouldn't increase standard here because we still want to check that tests pass in all previous standards.
Create a new test file `interfaces-global-init-cxx20.cpp` where you would place `-std=c++20-or-later`

https://github.com/llvm/llvm-project/pull/148334