[clang] [clang-scan-deps] Fix "unterminated conditional directive" bug (PR #146645)

[Ziqing Luo via cfe-commits]

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@@ -393,7 +393,7 @@ static bool isQuoteCppDigitSeparator(const char *const Start,
 }
 
 void Scanner::skipLine(const char *&First, const char *const End) {
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ziqingluo-90 wrote:

Yeah, this is much simpler.  Thank you!
This fix relies on the input source being valid (e.g., if the source code is so invalid that there are arbitrary characters following a line-continuation, there could still be problems).  Still, I think it is a fair assumption for `clang-scan-deps`.

https://github.com/llvm/llvm-project/pull/146645