Index: poco-1.11.0/Foundation/CMakeLists.txt
===================================================================
--- poco-1.11.0.orig/Foundation/CMakeLists.txt
+++ poco-1.11.0/Foundation/CMakeLists.txt
@@ -156,7 +156,7 @@ else()
 			elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD")
 				target_compile_definitions(Foundation PUBLIC POCO_HAVE_FD_POLL)
 				target_link_libraries(Foundation PUBLIC pthread ${CMAKE_DL_LIBS} rt)
-			elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "AIX")
+			elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "AIX" OR "${CMAKE_SYSTEM_NAME}" STREQUAL "GNU")
 				target_compile_definitions(Foundation PUBLIC _XOPEN_SOURCE=500 POCO_HAVE_FD_POLL)
 				target_link_libraries(Foundation PUBLIC pthread ${CMAKE_DL_LIBS} rt)
 			else()
