[clang] [llvm] [clang] Use separator for large numeric values in overflow diagnostic (PR #80939)

[Aaron Ballman via cfe-commits]

================
@@ -2223,9 +2227,14 @@ void APInt::toString(SmallVectorImpl<char> &Str, unsigned Radix, bool Signed,
       ++Prefix;
     };
 
+    int Pos = 0;
     while (N) {
+      if (insertSeparators && Pos % Grouping == 0 && Pos > 0) {
+        *--BufPtr = '\'';
+      }
----------------
AaronBallman wrote:

```suggestion
      if (insertSeparators && Pos % Grouping == 0 && Pos > 0)
        *--BufPtr = '\'';
```
Our coding style guideline is rather unintuitive in that it requires leaving braces off single-line substatements like this.

https://github.com/llvm/llvm-project/pull/80939