All non-x86 architectures need -pthread to link with threads enabled.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,7 +140,7 @@ TARGET_LINK_LIBRARIES(
 )
 ELSE()
 TARGET_LINK_LIBRARIES(
-        pgagent ${PG_LIBRARIES} ${Boost_LIBRARIES}
+        pgagent ${PG_LIBRARIES} ${Boost_LIBRARIES} -pthread
 )
 ENDIF()
 
