Adding an ios_kernel_extension rule

[YungRaj]

As per the new developments in being able to run virtual iPhones using Virtualization.framework, I was hoping we could add a new rule named ios_kernel_extension that would be effectively the same thing as macos_kernel_extension but be for building iOS kernel extensions for mobile platforms. Specifically for use on virtual iPhone environments for example

[YungRaj]

I can also submit a pull request to make this change if someone directs me to the right parts of the bazel apple rules that can help me implement this

[adincebic]

Personally I am not familiar with those kernel extensions for iOS. Do you mind attaching small example project @YungRaj ?

[YungRaj]

Right now the project I have is private. It's currently a macOS kernel extension that I know for sure can also be ported to iOS because it doesn't drive or touch hardware unique to either OS.

Kernel extensions typically aren't supported on iOS because Apple signs and verifies the kernelcache containing all precompiled kernel extensions during the boot process via e.g. SecureROM and iBoot. With that said, new developments that allow for the support of Virtual iPhones has been proven with Virtualization.framework with custom changes to the core ipsw artifacts. If we can bake our own kernel extension into the kernel cache (with custom tooling that I'll need to write of course) that is used to boot the iOS kernel on Virtualization.framework, then we will be able to load custom kernel extensions of our own.

My project uses bazel, so I was just hoping for a way to at least get the kernel extension that I built to build the kernel extension for iOS modulo any differences in the build process e.g. Xcode and the iOS/macOS SDKs that might be needed.

[YungRaj]

Update: I'll go ahead and start a pull request to make this work