[llvm] [FileCheck]: Fix diagnostics for NOT prefixes (PR #78412)

[Thomas Preud'homme via llvm-commits]

https://github.com/RoboTux commented:

Almost there, it's missing the printMatch() and printNoMatch() changes to use the prefix from DagNotPrefixInfo instead of the CheckString that called Check().

Also can you remove all the codestyle changes on lines not changed by you? You can use git diff -U0 | clang-format-diff.py -i p1 to only format your lines on a patch. clang-format-diff is in clang/tools/clang-format/clang-format-diff.py

https://github.com/llvm/llvm-project/pull/78412