Support modifying module metadata via JVM flags

[SquidDev]

Kotlin does a slightly cursed thing in its stdlib where it patches out one of its classes when a debugger is attached. However, the replacement class references things outside of the original module definition (yeah, I don't know why either >_>), which obviously causes IllegalAccessErrors at runtime.

The recommend solution for this is to use --add-reads to allow this access when running under a debugger. However, this only applies to the boot layer (the --add-xxx flags aren't even readable by user code!), and not modules defined by sjh.

It would be nice if spj supported similar functionality, though driven via system properties instead.