Looks like the dependency mechanism is broken in SDK 2.1.1/Win7. The .d files are being created but changes to headers are not triggering rebuilds as expected. This has bit me a couple of times.
The path in generated .d files is not correct.
To fix this change the definition of MAKE_DEP_FILE in WICED\Wiced-Smart\spar\gcc\rules_cm3_gcc.inc to:
MAKE_DEP_FILE = $(XCC) $(C_FLAGS) $(LIST_OPTIONS) -MM -MP -MF $(@:$(suffix $@)=.d) -MT $@ $<