lint/lintutil: only print relative paths if they're shorter
lint/lintutil: only print relative paths if they're shorter

Avoid printing paths like the following:

  ../../../../../../usr/lib/go/src/fmt/print.go

and instead only print relative paths when they're shorter than the
absolute paths.

This is taken directly from the go tool.

dominikh/go-tools,dominikh/go-tools,dominikh/go-tools,dominikh/go-tools