[llvm] Fix CI after #138708 (PR #140111)

[Aaron Ballman via llvm-commits]

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@@ -510,11 +510,15 @@ GTEST_API_ void PrintTo(wchar_t wc, ::std::ostream* os);
 
 GTEST_API_ void PrintTo(char32_t c, ::std::ostream* os);
 inline void PrintTo(char16_t c, ::std::ostream* os) {
-  PrintTo(ImplicitCast_<char32_t>(c), os);
+  // FIXME: the cast from char16_t to char32_t may be incorrect
+  // for a lone surrogate
+  PrintTo(static_cast<char32_t>(c), os);
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AaronBallman wrote:

Modifying third-party headers makes upgrading to newer versions much harder, are we sure we want to do that? What's the long-term plan?

https://github.com/llvm/llvm-project/pull/140111