[clang-tools-extra] [clang-tidy][NFC] Use universal utility mock in testcases [1/N] (PR #185431)

[Baranov Victor via cfe-commits]

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@@ -1,20 +1,8 @@
 // RUN: %check_clang_tidy -std=c++14-or-later %s cppcoreguidelines-missing-std-forward %t -- \
-// RUN: -config="{CheckOptions: {cppcoreguidelines-missing-std-forward.ForwardFunction: custom_forward}}" -- -fno-delayed-template-parsing
+// RUN: -config="{CheckOptions: {cppcoreguidelines-missing-std-forward.ForwardFunction: custom_forward}}" -- -isystem %clang_tidy_headers -fno-delayed-template-parsing
 
 // NOLINTBEGIN
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vbvictor wrote:

Not needed anymore?

https://github.com/llvm/llvm-project/pull/185431