Ignore certain folders from being matched

[tmayoff]

Since Github only shows 10 warnings in a run, it'd be nice if they were all from the actual project and not from a dependency, being able to ignore third_party, external, subprojects folders would be nice

[marauder2k7]

+1 i have a project with quite a few libs and all the warnings i am getting are from them and not my own code

[tmayoff]

I ended up creating my own problem matcher, this also adds the changes from here as well.

{
    "problemMatcher": [
        {
            "owner": "gcc-problem-matcher",
            "pattern": [
                {
                    "regexp": "^(..\/)(.*?)(?<!(subprojects|external|\/usr).*):(\\d+):(\\d*):?\\s+(?:fatal\\s+)?(warning|error):\\s+(.*)$",
                    "file": 2,
                    "line": 4,
                    "column": 5,
                    "severity": 6,
                    "message": 7
                }
            ]
        }
    ]
}