Windows: Fix security warning regression

Signed-off-by: John Howard <jhoward@microsoft.com>

api/client/build.go

@@ -265,8 +265,9 @@ func (cli *DockerCli) CmdBuild(args ...string) error {
 		}
 	}
 
-	// Windows: show error message about modified file permissions.
-	if response.OSType == "windows" {
+	// Windows: show error message about modified file permissions if the
+	// daemon isn't running Windows.
+	if response.OSType != "windows" && runtime.GOOS == "windows" {
 		fmt.Fprintln(cli.err, `SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.`)
 	}
 

integration-cli/docker_cli_build_test.go

@@ -4920,8 +4920,26 @@ func (s *DockerSuite) TestBuildNotVerboseSuccess(c *check.C) {
 		if outRegexp.Find([]byte(stdout)) == nil {
 			c.Fatalf("Test %s expected stdout to match the [%v] regexp, but it is [%v]", te.Name, outRegexp, stdout)
 		}
-		if stderr != "" {
-			c.Fatalf("Test %s expected stderr to be empty, but it is [%#v]", te.Name, stderr)
+		if runtime.GOOS == "windows" {
+			// stderr contains a security warning on Windows if the daemon isn't Windows
+			lines := strings.Split(stderr, "\n")
+			warningCount := 0
+			for _, v := range lines {
+				warningText := "SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host."
+				if strings.Contains(v, warningText) {
+					warningCount++
+				}
+				if v != "" && !strings.Contains(v, warningText) {
+					c.Fatalf("Stderr contains unexpected output line: %q", v)
+				}
+			}
+			if warningCount != 1 && daemonPlatform != "windows" {
+				c.Fatalf("Test %s didn't get security warning running from Windows to non-Windows", te.Name)
+			}
+		} else {
+			if stderr != "" {
+				c.Fatalf("Test %s expected stderr to be empty, but it is [%#v]", te.Name, stderr)
+			}
 		}
 	}