Fixed PSP compiling

src/thread/CMakeLists.txt

@@ -16,4 +16,9 @@ if(DUSK_TARGET_SYSTEM STREQUAL "linux")
     PRIVATE
       DUSK_THREAD_PTHREAD=1
   )
+elseif(DUSK_TARGET_SYSTEM STREQUAL "psp")
+  target_compile_definitions(${DUSK_TARGET_NAME}
+    PRIVATE
+      DUSK_THREAD_PTHREAD=1
+  )
 endif()