modules: properly handle implicit required inter-module dependencies.

modules/FindMagnum.cmake

@@ -314,6 +314,13 @@ foreach(_component ${Magnum_FIND_COMPONENTS})
         list(APPEND _MAGNUM_${_COMPONENT}_DEPENDENCIES Text TextureTools)
     endif()
 
+    # Mark the dependencies as required if the component is also required
+    if(Magnum_FIND_REQUIRED_${_component})
+        foreach(_dependency ${_MAGNUM_${_COMPONENT}_DEPENDENCIES})
+            set(Magnum_FIND_REQUIRED_${_dependency} TRUE)
+        endforeach()
+    endif()
+
     list(APPEND _MAGNUM_ADDITIONAL_COMPONENTS ${_MAGNUM_${_COMPONENT}_DEPENDENCIES})
 endforeach()