[include-cleaner] Don't apply PreferredHeader hings for standard headers.

[hokein]

Summary

Fixes https://github.com/llvm/llvm-project/issues/62635

[kadircet]

thanks!

clang-tools-extra/include-cleaner/lib/FindHeaders.cpp

while (Read != Headers.end() &&
       ++Read;
     }
   }
   Headers.erase(Write, Headers.end());
 
   // Add name match hints to deduplicated providers.
   llvm::StringRef SymbolName = symbolName(S);
   for (auto &H : Headers) {
+    // Don't apply name match hints to standard headers as the standard headers
+    // are already ranked in the stdlib mapping.
+    if (H.kind() == Header::Standard)
+      continue;
     if (nameMatch(SymbolName, H))
       H.Hint |= Hints::PreferredHeader;
   }
 
   // FIXME: Introduce a MainFile header kind or signal and boost it.
   return ranked(std::move(Headers));
 }
 } // namespace clang::include_cleaner

clang-tools-extra/include-cleaner/unittests/FindHeadersTest.cpp

for (const auto &T : TestCases) {
     Inputs.Code = T.Code;
     buildAST();
     EXPECT_THAT(headersFor(T.Name),
                 UnorderedElementsAre(
                     Header(*tooling::stdlib::Header::named(T.ExpectedHeader))));
   }
 }
 
+TEST_F(HeadersForSymbolTest, StandardHeaders) {
+  Inputs.Code = "void assert();";
+  buildAST();
+  EXPECT_THAT(
+      headersFor("assert"),
+      // Respect the ordering from the stdlib mapping.
+      UnorderedElementsAre(tooling::stdlib::Header::named("<cassert>"),
+                           tooling::stdlib::Header::named("<assert.h>")));
+}
+
+
 } // namespace
 } // namespace clang::include_cleaner