Check for WNOWAIT in waitpid() in runtime (not in cmake/configure) Because checking in cmake breaks cross-compiling. Introduced-in: 43eb56c7c738e3642f0981e3dd6ab9e082eec798. Fixes: #482 Fixes: #462 Refs: #475 v2: use waitid() with WNOWAIT v3: use WNOWAIT only if it available in waitpid(), because not all netbsd supports it