Warn about incorrect include paths in the compile command's file

[sean-mcmanus]

For my extension, I'm creating a better Backup Intellisense that parses the compile commands for includePaths which also lets you convert it to exclusive includePath Intellisense.

Doing so shows 88 include paths, in the compile commands file, that were incorrect. They must be not that important since Intellisense still worked.

Would this be considered a bug(or feature request) that the cpptools extension doesn't warn about incorrect include paths in the compile command's file?

Originally posted by @boocs in #6358 (comment)