[clang] Add some basic extra support for C++ unity building (PR #146104)

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github-actions[bot] wrote:

<!--LLVM CODE FORMAT COMMENT: {clang-format}-->


:warning: C/C++ code formatter, clang-format found issues in your code. :warning:

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You can test this locally with the following command:
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``````````bash
git-clang-format --diff HEAD~1 HEAD --extensions h,cpp -- clang/examples/JumboSupport/JumboSupport.cpp clang/include/clang/AST/Decl.h clang/lib/AST/ItaniumMangle.cpp clang/lib/Sema/SemaLookup.cpp
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<details>
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View the diff from clang-format here.
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``````````diff
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 17552c23d..2256d54f5 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -24,12 +24,12 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprConcepts.h"
-#include "clang/Basic/SourceManager.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/Mangle.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/ABI.h"
 #include "clang/Basic/Module.h"
+#include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/Thunk.h"
 #include "llvm/ADT/StringExtras.h"

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https://github.com/llvm/llvm-project/pull/146104