[clang] [Clang] Defaults `-Wunicode-whitespace` to an error. (PR #210945)

[Aaron Ballman via cfe-commits]

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@@ -7,8 +7,8 @@
 
 // This file contains Unicode characters; please do not "fix" them!
 
-extern int x; // expected-warning {{treating Unicode character as whitespace}}
-extern int　x; // expected-warning {{treating Unicode character as whitespace}}
+extern int x; // expected-error {{treating character <U+' ' U+00A0> as whitespace}}
+extern int　x; // expected-error {{treating character <U+'　' U+3000> as whitespace}}
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AaronBallman wrote:

`U+' '` looks really odd to me, we only want the second `U+` right?

https://github.com/llvm/llvm-project/pull/210945