Added integration test

internal/integrationtest/compile_3/compile_env_var_test.go

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+// This file is part of arduino-cli.
+//
+// Copyright 2024 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 compile_test
+
+import (
+	"testing"
+
+	"github.com/arduino/arduino-cli/internal/integrationtest"
+	"github.com/arduino/go-paths-helper"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCompileEnvVarOnNewProcess(t *testing.T) {
+	// See: https://github.com/arduino/arduino-cli/issues/2499
+
+	env, cli := integrationtest.CreateArduinoCLIWithEnvironment(t)
+	defer env.CleanUp()
+
+	// Run update-index with our test index
+	_, _, err := cli.Run("core", "install", "arduino:[email protected]")
+	require.NoError(t, err)
+
+	// Prepare sketchbook and sketch
+	sketch, err := paths.New("testdata", "bare_minimum").Abs()
+	require.NoError(t, err)
+
+	// Build "printenv" helper insider testdata/printenv
+	printenvDir, err := paths.New("testdata", "printenv").Abs()
+	require.NoError(t, err)
+	builder, err := paths.NewProcess(nil, "go", "build")
+	require.NoError(t, err)
+	builder.SetDir(printenvDir.String())
+	require.NoError(t, builder.Run())
+	printenv := printenvDir.Join("printenv")
+
+	// Patch avr core to run printenv instead of size
+	plTxt, err := cli.DataDir().Join("packages", "arduino", "hardware", "avr", "1.8.6", "platform.txt").Append()
+	require.NoError(t, err)
+	_, err = plTxt.WriteString("recipe.size.pattern=" + printenv.String() + "\n")
+	require.NoError(t, err)
+	require.NoError(t, plTxt.Close())
+
+	// Run compile and get ENV
+	_, stderr, err := cli.Run("compile", "-v", "-b", "arduino:avr:uno", sketch.String())
+	require.NoError(t, err)
+	require.Contains(t, string(stderr), "ENV> ARDUINO_USER_AGENT=")
+}

internal/integrationtest/compile_3/testdata/printenv/.gitignore

@@ -0,0 +1 @@
+printenv

internal/integrationtest/compile_3/testdata/printenv/main.go

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+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	for _, env := range os.Environ() {
+		fmt.Fprintln(os.Stderr, "ENV>", env)
+	}
+}