[clang] [Clang] fix crash by avoiding invalidation of extern main declaration during strictness checks (PR #104594)

[Alexander Kornienko via cfe-commits]

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@@ -264,6 +264,7 @@ Bug Fixes to C++ Support
 - Properly reject defaulted copy/move assignment operators that have a non-reference explicit object parameter.
 - Clang now properly handles the order of attributes in `extern` blocks. (#GH101990).
 - Fixed an assertion failure by preventing null explicit object arguments from being deduced. (#GH102025).
+- Fixed a crash caused by marking the function declaration as invalid during strictness checks on ``extern`` main. (#GH104570).
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alexfh wrote:

Is it actually necessary, given that the issue was introduced in the same release?

https://github.com/llvm/llvm-project/pull/104594