How do I access secrets in build.gradle?

I need to access secrets in my app `build.gradle`, but I'm not seeing any documentation on how to do it. Specifically, I want to default my signing keystore to use an environment variable if present for github actions, but then fallback to using a local secrets file. It seems like this would probably be supported, is there a way to do this?

I'm trying this, but this doesn't work:
```
signingConfigs {
release {
storePassword System.getenv("MY_RELEASE_KEYSTORE_PASSWORD") ?: project.findProperty('MyReleaseKeystorePassword')
}
}
```