private boolean isExistingArg(String s) {
		return Arrays.stream(Arg.values()).anyMatch(e -> e.matches(s));
	}
Prints out the usage details and exits the Java application with an exit code that
indicates error.

@param execCmd the command used to run the headless analyzer from the calling method.
Ghidra/Features/Base/src/main/java/ghidra/app/util/headless/AnalyzeHeadless.java