plugins/clangtidy: fix problem pattern to also match windows paths

A path may now start either with 'X:\' or '/'
1 job for !185 with clang-tidy-windows in 101 minutes and 7 seconds (queued for 80 minutes and 12 seconds)
detached
Status Job ID Name Coverage
  Build
failed #74354
linux kf5-qt5 qt5.12

01:41:07

47.0%
 
Name Stage Failure
failed
linux kf5-qt5 qt5.12 Build
build: found 16463 matching files and directories  
WARNING: Uploading artifacts as "archive" to coordinator... failed id=74354 responseStatus=502 Bad Gateway status=502 token=VsLSq9fA
WARNING: Retrying... context=artifacts-uploader error=invalid argument
WARNING: Uploading artifacts as "archive" to coordinator... failed id=74354 responseStatus=502 Bad Gateway status=502 token=VsLSq9fA
WARNING: Retrying... context=artifacts-uploader error=invalid argument
WARNING: Uploading artifacts as "archive" to coordinator... failed id=74354 responseStatus=502 Bad Gateway status=502 token=VsLSq9fA
FATAL: invalid argument
Cleaning up file based variables
ERROR: Job failed: exit code 1