Check for source vs publish path to not be same location

[talves]

Before I start, promise not to laugh (too hard).

Issue

1. Copied the example hello.js into the functions folder
2. Made a scripts command in package.json called start : "start": "netlify-lambda serve functions"
3. netlify.toml has functions = "functions" under the build

When running the yarn start command, the build picks up the source and start overwriting with the bundle. It watches and builds again, causing an infinite loop.

Expected behavior

Would be great to get a message "source and publish folder should be in different locations"