main_test: Fix "gopath mode" detection in projectRoot() (#1426)

* main_test: Fix "gopath mode" detection in projectRoot()

Fails detect that this is a "gopath mode" when GOPATH contains several paths ex. "d:\\dir\\gopath;f:\\dir\\gopath2"

cmd/dlv/dlv_test.go

@@ -51,8 +51,13 @@ func projectRoot() string {
 	if err != nil {
 		panic(err)
 	}
-	if strings.Contains(wd, os.Getenv("GOPATH")) {
-		return filepath.Join(os.Getenv("GOPATH"), "src", "github.com", "derekparker", "delve")
+
+	gopaths := strings.FieldsFunc(os.Getenv("GOPATH"), func(r rune) bool { return r == os.PathListSeparator })
+	for _, curpath := range gopaths {
+		// Detects "gopath mode" when GOPATH contains several paths ex. "d:\\dir\\gopath;f:\\dir\\gopath2"
+		if strings.Contains(wd, curpath) {
+			return filepath.Join(curpath, "src", "github.com", "derekparker", "delve")
+		}
 	}
 	val, err := exec.Command("go", "list", "-m", "-f", "{{ .Dir }}").Output()
 	if err != nil {