Update CPUSummary.jl

Author: ChrisRackauckas

src/CPUSummary.jl

@@ -54,8 +54,8 @@ else
   include("generic_topology.jl")
 end
 # Load preferences at compile time with exact same names as __init__
-const nc = @load_preference("nc", nothing)
-const syst = @load_preference("syst", nothing)
+const nc = @load_preference("nc", _get_num_cores())
+const syst = @load_preference("syst", Sys.CPU_THREADS)
 num_l1cache() = static(nc)
 num_cores() = static(nc)
 sys_threads() = static(syst)