Bug 481098

SUMMARY
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On a high level kdesrc-build populates the two variables "num-cores" and "num-cores-low-mem" inside the kdesrc-buildrc config file like so:
num-cores = Result of nproc
num-cores-low-mem = min(num-cores, Total ram in GiB / 2GiB )

It does so only if it detects that the current platform is linux or freebsd. However, the platform detection logic is flawed on the linux side because it's relying on the OS identification parameter "ID" from /etc/os-release and testing if it's equal to "linux". On some (most?) distributions this is not the case and the script will default to assigning the value 4 to num-cores and num-cores-low-mem.
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STEPS TO REPRODUCE
0. Temporarily backup and move/delete ~/.config/kdesrc-buildrc if it exists
1. Run through "./kdesrc-build --initial-setup" 

OBSERVED RESULT
The variables num-cores and num-cores-low-mem inside ~/.config/kdesrc-buildrc will have the default value of 4 when running on a distribution which sets the "ID" paramenter of /etc/os-release to something other than "linux".

EXPECTED RESULT
The variables should be set based on the amount of system memory. A 16-core 16GiB Ram System should have the following values: num-cores = 16; num-cores-low-mem = 8.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora Linux 39
(available in About System)
KDE Plasma Version: 5.27.10
KDE Frameworks Version: 5.113.0
Qt Version: 5.15.12

ADDITIONAL INFORMATION
The relevant code starts here
https://invent.kde.org/sdk/kdesrc-build/-/blob/master/modules/ksb/FirstRun.pm?ref_type=heads#L299