Terminate owned subprocess trees

internal/adapters/subprocess/process_tree_unsupported.go

@@ -0,0 +1,12 @@
+//go:build !linux && !darwin && !windows
+
+package subprocess
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func newOwnedProcessTree() (ownedProcessTree, error) {
+	return nil, fmt.Errorf("owned subprocess trees are unsupported on %s", runtime.GOOS)
+}