systemd oneshot Requirement to execute only once

I have multiple systemd services that require a generated EnvironmentFile. I have a shell script which generates this Environment file, but since I need that environment file before any Exec… commands execute, I cannot use ExecStartPre=generate_env_file.sh . Therefore, I have another service (generate_env_file.service) set to run that script as a oneshot:

[Service]
Type=oneshot
ExecStartPre=/usr/bin/touch /path/to/config.ini
ExecStart=/path/to/generate_env_file.sh

and I have multiple other service files which have:

[Unit]
Requires=generate_env_file.service
After=generate_env_file.service

How can I guarantee that two or more dependent services (which require generate_env_file.service) will not run in parallel and spawn two parallel executions of generate_env_file.service?

I’ve looked at using RemainAfterExit=true or possibly StartLimitIntervalSec= and StartLimitBurst= to ensure that only one copy will execute at a time during some period but I’m not sure the best way to go about doing this.