ltimer: enable timer for QEMU Arm arch timers

[midnightveil]

The if statements were not strictly equivalent and broke the camkes timer component builds:

https://github.com/seL4/util_libs/pull/196/files#r2178857087

Ref: seL4/sel4test#142

[lsf37]

It looks to me like this change is semantically equivalent to what was there before.

If SIMULATION is set, it'll still set LibPlatSupportHaveTimer to OFF, and the CAmkES build does have SIMULATION set by default, i.e. we will see it also for platforms like tx2, imx8mm, etc.

I'm tending towards changing the camkes default setting, tbh. It doesn't really make sense to me to have simulation settings on for hardware images.

It is possible that we had a policy that setting simulation to "on" shouldn't break things on hardware, but I don't remember anything in that direction. Maybe @kent-mcleod remembers?

[Indanz]

I think it would be better to remove the SIMULATION part of the check than shuffling this bit around like this.

[axel-h]

As a general question, why are we explicitly checking for KernelPlatformQEMUArmVirt here actually, can't this be made KernelArchARM to make this generic?

Below in line 124 there is this, which make we wonder why we don't check KernelPlatformQuartz64/KernelPlatformIMX93 here then also

if(KernelPlatformQEMUArmVirt OR KernelPlatformQuartz64 OR KernelPlatformIMX93)
    if(KernelArmExportPCNTUser AND KernelArmExportPTMRUser)
        list(APPEND deps src/arch/arm/generic_ltimer.c)
    endif()
endif()