fix: preserve process.execArgv

[jsjoeio]

This ensures flags like --prof are passed down to the vs code process so we can profile everything.

To test this:

1. run ./lib/node --prof .
2. in another terminal, run ps -ejww

You should see --prof next to every vs code process.

P.S. this approach leans on a pattern already in the codebase:

vscode/src/vs/base/parts/ipc/node/ipc.cp.ts

Lines 198 to 200 in 06bd7ae

	// if not set, the forked process inherits the execArgv of the parent process
	// --inspect and --inspect-brk can not be inherited as the port would conflict
	forkOpts.execArgv = process.execArgv.filter(a => !/^--inspect(-brk)?=/.test(a)); // remove

[jsjoeio]

@alexdima any update on this? happy to open an issue if you'd like more context first.

[alexdima]

Thank you!