clang-tidy: ignore -Wunknown-pragmas temporarily

Bug: b:382774818
Change-Id: I6abffbeace92fea7465de72f8bb9aabbe1963ff7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6150080
Reviewed-by: Peter Kasting <[email protected]>
Commit-Queue: Peter Kasting <[email protected]>
Commit-Queue: George Burgess <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1402635}

Author: gburgessiv

.clang-tidy

@@ -71,4 +71,9 @@
     # https://clang.llvm.org/extra/clang-tidy/checks/misc/include-cleaner.html
     - key: misc-include-cleaner.IgnoreHeaders
       value:        (gmock/gmock|gtest/gtest|third_party|build/linux/debian).*
+
+  ExtraArgs:
+    # b/382774818: disable unknown pragma warnings until we can figure out why
+    # unknown pragmas are being warned about.
+    - -Wno-unknown-pragmas
 ...