Pass all environment variables to the Docker CLI

Fixes: #35

tools/src/docker/docker.go

@@ -9,7 +9,6 @@ import (
 	"os"
 	"os/exec"
 	"regexp"
-	"strings"
 	"syscall"
 )
 
@@ -124,18 +123,11 @@ func ImagePull(image string) error {
 }
 
 func Docker(arg ...string) error {
-	var env []string
-
 	cmd, err := exec.LookPath(dockerCmd[0])
 	if err != nil {
 		return err
 	}
 	args := append(dockerCmd, arg...)
 
-	for _, e := range os.Environ() {
-		if strings.HasPrefix(e, "DOCKER_") {
-			env = append(env, e)
-		}
-	}
-	return syscall.Exec(cmd, args, env)
+	return syscall.Exec(cmd, args, os.Environ())
 }