Fix linking of cmcurl on Solaris 10 due to clock_gettime() in rt
Cross compiling (probably also for native) CMake for Solaris 10, -lrt is needed to successfully link cmcurl. https://docs.oracle.com/cd/E26505_01/html/816-5171/clock-gettime-3rt.html
Cross compiling (probably also for native) CMake for Solaris 10, -lrt is needed to successfully link cmcurl. https://docs.oracle.com/cd/E26505_01/html/816-5171/clock-gettime-3rt.html