allow config of the vet flag for go test

[topherbullock]

This is useful when running ginkgo against go code built pre-1.11, when vet wasn't run by default by go test

[williammartin]

Can you add a test for this please. Something like:

diff --git a/ginkgo/testrunner/test_runner_test.go b/ginkgo/testrunner/test_runner_test.go
index 6919170..92f1c1f 100644
--- a/ginkgo/testrunner/test_runner_test.go
+++ b/ginkgo/testrunner/test_runner_test.go
@@ -32,6 +32,7 @@ var _ = Describe("TestRunner", func() {
      "coverpkg":         strAddr(""),
      "cover":            boolAddr(false),
      "blockprofilerate": intAddr(100),
+     "vet":              strAddr("off"),
    }
    tr := testrunner.New(testsuite.TestSuite{}, 1, false, 0, opts, []string{})

@@ -50,6 +51,7 @@ var _ = Describe("TestRunner", func() {
      "-asmflags=a",
      "-pkgdir=b",
      "-gcflags=c",
+     "-vet=off",
    }))
  })
 })

[williammartin]

@topherbullock Can you please update this with tests?