Always pipe stdout/err/in when running tools.

This is required because some tools detects if the program is running
from terminal by looking at the stdin/out bindings.

Fix: #844

Author: cmaglie

Diff for: executils/executils.go

@@ -81,5 +81,12 @@ func Command(args []string) (*exec.Cmd, error) {
 	}
 	cmd := exec.Command(args[0], args[1:]...)
 	TellCommandNotToSpawnShell(cmd)
+
+	// This is required because some tools detects if the program is running
+	// from terminal by looking at the stdin/out bindings.
+	// https://github.com/arduino/arduino-cli/issues/844
+	cmd.Stdout = NullWriter
+	cmd.Stderr = NullWriter
+	cmd.Stdin = NullReader
 	return cmd, nil
 }

Diff for: executils/null.go

@@ -0,0 +1,36 @@
+// This file is part of arduino-cli.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to [email protected].
+
+package executils
+
+import "io"
+
+// NullReader is an io.Reader that will always return EOF
+var NullReader = &nullReader{}
+
+type nullReader struct{}
+
+func (r *nullReader) Read(buff []byte) (int, error) {
+	return 0, io.EOF
+}
+
+// NullWriter is an io.Writer that discards any output
+var NullWriter = &nullWriter{}
+
+type nullWriter struct{}
+
+func (r *nullWriter) Write(buff []byte) (int, error) {
+	return len(buff), nil
+}