We need to add find_package(Threads) to Source/cmake/WebKitCommon.cmake to make it link correctly like I needed to do in bug 167313.
Created attachment 299528 [details] Patch
Comment on attachment 299528 [details] Patch If this is only needed on Linux, should this be in WebKitCommon? Are you using the GTK port?
I found the error in my end with my Cmake options. This is a different Linux port.