We have a warning in sc_spawn given that stack size setting is not supported. However, as is a common call in SystemC, the warning generates too many logs for users. This CL changes it to be warn_once. Change-Id: I63c057ca99f68585303cf2b4fdddee5b713f856b Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60750 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Maintainer: Jason Lowe-Power <power.jg@gmail.com> Reviewed-by: Gabe Black <gabe.black@gmail.com> Reviewed-by: Yu-hsin Wang <yuhsingw@google.com> Tested-by: kokoro <noreply+kokoro@google.com>