py: Rebuild port if mpconfigport.mk changed (if any).

mpconfigport.mk contains configuration options which affect the way
MicroPython is linked. In this regard, it's "stronger" configuration
dependency than even mpconfigport.h, so if we rebuild everything on
mpconfigport.h change, we certianly should of that on mpconfigport.mk
change too.

py/py.mk

@@ -131,13 +131,17 @@ FORCE:
 $(HEADER_BUILD)/mpversion.h: FORCE | $(HEADER_BUILD)
 	$(Q)$(PYTHON) $(PY_SRC)/makeversionhdr.py $@
 
+# mpconfigport.mk is optional, but changes to it may drastically change
+# overall config, so they need to be caught
+MPCONFIGPORT_MK = $(wildcard mpconfigport.mk)
+
 # qstr data
 
 # Adding an order only dependency on $(HEADER_BUILD) causes $(HEADER_BUILD) to get
 # created before we run the script to generate the .h
 # Note: we need to protect the qstr names from the preprocessor, so we wrap
 # the lines in "" and then unwrap after the preprocessor is finished.
-$(HEADER_BUILD)/qstrdefs.generated.h: $(PY_QSTR_DEFS) $(QSTR_DEFS) $(PY_SRC)/makeqstrdata.py mpconfigport.h $(PY_SRC)/mpconfig.h | $(HEADER_BUILD)
+$(HEADER_BUILD)/qstrdefs.generated.h: $(PY_QSTR_DEFS) $(QSTR_DEFS) $(PY_SRC)/makeqstrdata.py mpconfigport.h $(MPCONFIGPORT_MK) $(PY_SRC)/mpconfig.h | $(HEADER_BUILD)
 	$(ECHO) "GEN $@"
 	$(Q)cat $(PY_QSTR_DEFS) $(QSTR_DEFS) | $(SED) 's/^Q(.*)/"&"/' | $(CPP) $(CFLAGS) - | sed 's/^"\(Q(.*)\)"/\1/' > $(HEADER_BUILD)/qstrdefs.preprocessed.h
 	$(Q)$(PYTHON) $(PY_SRC)/makeqstrdata.py $(HEADER_BUILD)/qstrdefs.preprocessed.h > $@