.clang-tidy: ignore system headers from misc-include-cleaner

It seems that we don't want to add/remove system headers in some cases.
e.g.
https://crrev.com/c/5524195/5/crypto/nss_key_util.cc

Bug: 336474469
Change-Id: I56b4239832a5246cb6edb39bf6397ceb03e0a003
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5528895
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1299890}

Author: Takuto Ikuta

.clang-tidy

@@ -66,7 +66,9 @@
       value:        base/containers/adapters.h
     # Exclude some third_party headers from modification as file paths are not
     # starting from repository root in replacement suggestion.
+    # 'build/linux/debian' excludes system headers as they don't have
+    # appropriate IWYU pragmas.
     # https://clang.llvm.org/extra/clang-tidy/checks/misc/include-cleaner.html
     - key: misc-include-cleaner.IgnoreHeaders
-      value:        (gmock/gmock|gtest/gtest|third_party).*
+      value:        (gmock/gmock|gtest/gtest|third_party|build/linux/debian).*
 ...