Check for existance of CPU_COUNT macro before using it.
Check for existance of CPU_COUNT macro before using it.

This resolves #485.

wqfish/jemalloc,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,wqfish/jemalloc,wqfish/jemalloc,jemalloc/jemalloc-cmake,wqfish/jemalloc,wqfish/jemalloc,jemalloc/jemalloc-cmake