Environment variable `SHM_ID` is not passed to the engine in startup tests

[CSharperMantle]

Fuzzing SpiderMonkey currently produces this warning at the beginning:

[Fuzzer] Initialized
[Fuzzer] Recommended timeout: [...]
[Fuzzer] Runner has non-empty output for empty program! This might indicate that some flags are wrong.
[Fuzzer] Output:
[COV] no shared memory bitmap available, skipping
[COV] edge counters initialized. Shared memory: (null) with 398403 edges

This is because the environment variable SHM_ID is not passed to the engine when running startup tests. While this does not currently pose a problem, this could be bad if some engine depends on the existence of shared memory for coverage in the future.

Related code:

fuzzilli/Sources/Fuzzilli/Util/JavaScriptExecutor.swift

Lines 93 to 99 in 11402cc

	let task = Process()
	task.standardOutput = outputPipe
	task.standardError = errorPipe
	task.arguments = arguments + [url.path]
	task.executableURL = URL(fileURLWithPath: path)
	task.standardInput = inputPipe
	try task.run()