$OpenBSD$

no -ldl on OpenBSD, but we need -lpthread

Index: src/engine/CMakeLists.txt
--- src/engine/CMakeLists.txt.orig
+++ src/engine/CMakeLists.txt
@@ -76,7 +76,7 @@ else()
     system/i_cpu_posix.cc)
 
   set(PLATFORM_LIBRARIES
-    dl
+    pthread
     m)
 
 endif()
