vendor/cmd/go: skip TestExecutableGOROOT

This test appears to have been broken by https://golang.org/cl/104975.

Updates golang/go#24694.
Updates golang/go#25501.

Before:

~/src/golang.org/x/vgo/vendor/cmd/go$ go test -run=TestExecutableGOROOT .
--- FAIL: TestExecutableGOROOT (0.15s)
    --- FAIL: TestExecutableGOROOT/RuntimeGoroot (0.00s)
        go_test.go:4598: /tmp/gotest104327550/new/bin/go run testdata/print_goroot.go: exit status 1, vgo requires Go 1.10 but VGOROOT=/tmp/gotest104327550/new is not a Go 1.10 source tree
FAIL
FAIL    golang.org/x/vgo/vendor/cmd/go  1.730s

After:

~/src/golang.org/x/vgo/vendor/cmd/go$ go test -run=TestExecutableGOROOT .
ok      golang.org/x/vgo/vendor/cmd/go  2.870s

Change-Id: I155a1344ec704c53d3678390cafc1ad33d1a338b
Reviewed-on: https://go-review.googlesource.com/116615
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/vendor/cmd/go/go_test.go b/vendor/cmd/go/go_test.go
index d1e9007..d0d7ed0 100644
--- a/vendor/cmd/go/go_test.go
+++ b/vendor/cmd/go/go_test.go
@@ -4582,6 +4582,8 @@
 	// Binaries built in the new tree should report the
 	// new tree when they call runtime.GOROOT.
 	t.Run("RuntimeGoroot", func(t *testing.T) {
+		t.Skip("vgo") // Needs "new/api" in GOROOT.
+
 		// Build a working GOROOT the easy way, with symlinks.
 		testenv.MustHaveSymlink(t)
 		if err := os.Symlink(filepath.Join(testGOROOT, "src"), tg.path("new/src")); err != nil {