Fix Sokol on Linux

Author: NathanaelA

external/sokol/CMakeLists.txt

@@ -34,6 +34,7 @@ else ()
     add_library(sokol STATIC sokol.c ${SOKOL_HEADERS})
     if (CMAKE_SYSTEM_NAME STREQUAL Linux)
         target_link_libraries(sokol INTERFACE X11 Xi Xcursor GL dl m)
+        find_package(Threads)
         target_link_libraries(sokol PUBLIC Threads::Threads)
     endif ()
 endif ()