iOS environment variable support

[Jasper-Bekkers]

This is quite hacky; but it enables the metal debug layer (by default). This same code could be used to add other environment variables.

Probably shouldn't be merged as-is.

[kali]

Mmm.. is this a way to set arbitrary env variables for the app process on the device ? Because IIRC dinghy expose a more or less generic way to do that from configuration that we never managed to get working for iOS through lldb... Could we consider binding it to this trick ?

[Jasper-Bekkers]

Yeah this is the way to set regular environment variables on iOS processes through lldb so you should be able to use this for that.

[kali]

It looks relatively straightforward if you feel like doing the patch, all in dinghy-lib/src/ios/device.rs: _envs is ignore in one or two places and should be pass down to the function that generates the lldb script...

[Jasper-Bekkers]

I can take a quick look.

[Jasper-Bekkers]

I think these changes ought to do it (at least for me they give me the right env vars now when launching for example with --env={"RUST_BACKTRACE=1","TEST=23"}).

[kali]

0.4.39 pushed ! enjoy ! thanks for the patch !