USERSPACE and CMAKE_LINKER_GENERATOR

[RobinKastberg]

To Reproduce
Try to build any application/test with CONFIG_USERSPACE=y and CONFIG_CMAKE_LINKER_GENERATOR=y

Expected behavior
Working

Impact
This will cause problems if you want to use USERSPACE together with armclang or IAR toolchain.

Logs and console output

user@b7f43aa2a597:/workdir/zephyr$ scripts/twister -T samples/hello_world/ -x CMAKE_LINKER_GENERATOR=y -x CONFIG_USERSPACE=y
Renaming output directory to /workdir/zephyr/twister-out.1
INFO    - Using Ninja..
INFO    - Zephyr version: v4.0.0-4635-g2fc39ec3f35a
INFO    - Using 'zephyr' toolchain.

Currently, we (IAR) are working with a two pronged approach

1. is getting tests: kconfig: cmake: Disable USERSPACE when using LINKER_GENERATOR #85075 into main. This will make IAR twister tests go green without spurious failures because of this.
2. is getting Make CONFIG_USERSPACE=y and CONFIG_CMAKE_LINKER_GENERATOR=y work together #85241 into main. This will make CMAKE_LINKER_GENERATOR+USERSPACE work for ld, and the workaround above can be reverted/closed (or made more toolchain specific).