BulkUpdateEnv returns a new slice suitable for use with exec.Cmd.Env based on env but with environment variables for the keys in update added/changed to the values in update.

IsTruthyEnv return true if name is set in the environment and has value other than 0 or false (case-insensitive).

UpdateEnv takes an environment array, an env var name, and an environment var value and updates the current definition of the env var or adds a new environment variable definition.