electron build breaks if invest --version produces extra stdout

[emlys]

The workbench build with electron-builder runs the invest --version command to get the version string used later in the build:

invest/workbench/electron-builder-config.js

Lines 8 to 10 in 1c98e3a

	const investVersion = execFileSync(
	'../dist/invest/invest', ['--version']
	).toString().trim();

If the command writes anything extra to stdout, the version string is invalid and the build fails. This is happening right now - I haven't identified the root cause yet, but swig/python detected a memory leak of type 'OSRSpatialReferenceShadow *', no destructor found. is being printed after the version. I recall the same issue happening once before. While this bug should be fixed, it doesn't need to break the electron build process.

Improve how we extract the version string to reduce chances of it being corrupted like this - maybe sufficient to just use the first line of output?