[clang] [Clang] Allow raw string literals in C as an extension (PR #88265)

[via cfe-commits]

Sirraide wrote:

So, apparently, this test here 
https://github.com/llvm/llvm-project/blob/cb76896d6e45e2c9b7ef5e47b6ec37aeca43f7a8/clang/unittests/Lex/DependencyDirectivesScannerTest.cpp#L586-L589

is now failing, presumably because of this:

https://github.com/llvm/llvm-project/blob/cb76896d6e45e2c9b7ef5e47b6ec37aeca43f7a8/clang/lib/Lex/DependencyDirectivesScanner.cpp#L71-L79

I’m not entirely sure how to fix this candidly. It doesn’t look like unconditionally enabling raw string literals is an option here... This situation reminds me of a similar issue we’re having with `'` in numeric literals (#88896). I’m personally not too familiar with the lexer, but would it be possible to pass through the original lang options here from wherever this is invoked?

https://github.com/llvm/llvm-project/pull/88265