feat: add agent exec pkg (#15577)

agent/agentexec/cmdtest/main_linux.go

@@ -0,0 +1,19 @@
+//go:build linux
+// +build linux
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/coder/coder/v2/agent/agentexec"
+)
+
+func main() {
+	err := agentexec.CLI()
+	if err != nil {
+		_, _ = fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}