Fixed|CMake: libgui is dependent on Assimp

This will ensure that Assimp is fully built before libgui. CMake doesn't
see this dependency automatically because of the "libassimp" interface
target, which uses the "assimp" target's output files but can't as such
be declared to be dependent on it.

doomsday/sdk/libgui/CMakeLists.txt

@@ -83,4 +83,9 @@ endif ()
 
 deng_deploy_library (libgui DengGui)
 
+# If Assimp is part of the build, ensure that it gets compiled before libgui.
+if (TARGET assimp)
+    add_dependencies (libgui assimp)
+endif ()
+
 deng_cotire (libgui src/precompiled.h)