Detect thread libs using CMake
Detect thread libs using CMake

Instead of hard-coding `-lpthread`, let CMake detect the proper options.
This will help minimize the number of changes required to support
additional OSes.

amelmquist/chrono,armanpazouki/chrono,Milad-Rakhsha/chrono,jcmadsen/chrono,projectchrono/chrono,dariomangoni/chrono,jcmadsen/chrono,rserban/chrono,jcmadsen/chrono,rserban/chrono,amelmquist/chrono,jcmadsen/chrono,armanpazouki/chrono,dariomangoni/chrono,andrewseidl/chrono,tjolsen/chrono,jcmadsen/chrono,jcmadsen/chrono,tjolsen/chrono,rserban/chrono,hsu/chrono,Bryan-Peterson/chrono,projectchrono/chrono,Bryan-Peterson/chrono,amelmquist/chrono,PedroTrujilloV/chrono,amelmquist/chrono,Bryan-Peterson/chrono,hsu/chrono,PedroTrujilloV/chrono,projectchrono/chrono,rserban/chrono,armanpazouki/chrono,hsu/chrono,PedroTrujilloV/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,rserban/chrono,Milad-Rakhsha/chrono,hsu/chrono,projectchrono/chrono,andrewseidl/chrono,tjolsen/chrono,armanpazouki/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,PedroTrujilloV/chrono,amelmquist/chrono,Milad-Rakhsha/chrono,andrewseidl/chrono,andrewseidl/chrono,andrewseidl/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,amelmquist/chrono,jcmadsen/chrono,dariomangoni/chrono,Bryan-Peterson/chrono,hsu/chrono,Bryan-Peterson/chrono,rserban/chrono,tjolsen/chrono,rserban/chrono,dariomangoni/chrono,armanpazouki/chrono,PedroTrujilloV/chrono,armanpazouki/chrono,tjolsen/chrono,dariomangoni/chrono