[rootless] Do not use libroot when targeting the simulator

[leptos-null]

What does this implement/fix? Explain your changes.

libroot is not compiled for the simulator.
To match this availability, use the fallback rootless macros when compiling for the simulator.

Checklist

• New code follows the code rules
• I've added modulemaps for any new libraries (e.g. see libactivator/module.modulemap): it should be possible to @import MyLibrary; in ObjC, or import MyLibrary in Swift.
• My contribution is code written by myself from reverse-engineered headers, licensed into the Public Domain as per LICENSE.md; or, code written by myself / taken from an existing project, released under an OSI-approved license, and I've added relevant licensing credit to LICENSE.md

Does this close any currently open issues?

No

Any relevant logs, error output, etc?

Any other comments?

No

Where has this been tested?

Operating System: macOS 15.3

Platform: Darwin

Target Platform: iphone, simulator

Toolchain Version: Apple clang version 16.0.0 (clang-1600.0.26.6)

SDK Version: 18.2

[saltman007web]

commit