Fixed sporadic IO copy error on CI

The StdoutPipe command explicitly mandate to not call proc.Wait before
the pipe is fully copied.

> StdoutPipe returns a pipe that will be connected to the command's
> standard output when the command starts.
>
> Wait will close the pipe after seeing the command exit, so most callers
> don't need to close the pipe themselves. It is thus incorrect to call
> Wait before all reads from the pipe have completed. For the same reason,
> it is incorrect to call Run when using StdoutPipe.

Author: cmaglie

internal/integrationtest/arduino-cli.go

@@ -389,22 +389,22 @@ func (cli *ArduinoCLI) run(ctx context.Context, stdoutBuff, stderrBuff io.Writer
 
 	cli.t.NoError(cliProc.Start())
 
+	if stdoutBuff == nil {
+		stdoutBuff = io.Discard
+	}
+	if stderrBuff == nil {
+		stderrBuff = io.Discard
+	}
 	var wg sync.WaitGroup
 	wg.Add(2)
 	go func() {
 		defer wg.Done()
-		if stdoutBuff == nil {
-			stdoutBuff = io.Discard
-		}
 		if _, err := io.Copy(stdoutBuff, io.TeeReader(stdout, terminalOut)); err != nil {
 			fmt.Fprintln(terminalOut, color.HiBlackString("<<< stdout copy error:"), err)
 		}
 	}()
 	go func() {
 		defer wg.Done()
-		if stderrBuff == nil {
-			stderrBuff = io.Discard
-		}
 		if _, err := io.Copy(stderrBuff, io.TeeReader(stderr, terminalErr)); err != nil {
 			fmt.Fprintln(terminalErr, color.HiBlackString("<<< stderr copy error:"), err)
 		}
@@ -416,8 +416,8 @@ func (cli *ArduinoCLI) run(ctx context.Context, stdoutBuff, stderrBuff io.Writer
 			}
 		}()
 	}
-	cliErr := cliProc.WaitWithinContext(ctx)
 	wg.Wait()
+	cliErr := cliProc.WaitWithinContext(ctx)
 
 	return cliErr
 }