cdx56: prepare to enable ulab

This involves fixing support for SRC_MOD and enabling INTERNAL_LIBM
including adding support for SRC_LIBM.

Author: jepler

ports/cxd56/Makefile

@@ -176,6 +176,10 @@ OBJ = $(PY_O) $(SUPERVISOR_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_S:.s=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_COMMON_HAL_EXPANDED:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_SHARED_MODULE_EXPANDED:.c=.o))
+ifeq ($(INTERNAL_LIBM),1)
+OBJ += $(addprefix $(BUILD)/, $(SRC_LIBM:.c=.o))
+endif
+OBJ += $(addprefix $(BUILD)/, $(SRC_MOD:.c=.o))
 
 # List of sources for qstr extraction
 SRC_QSTR += $(SRC_C) $(SRC_SUPERVISOR) $(SRC_COMMON_HAL_EXPANDED) $(SRC_SHARED_MODULE_EXPANDED)

ports/cxd56/mpconfigport.mk

@@ -18,3 +18,5 @@ CIRCUITPY_NEOPIXEL_WRITE = 0
 CIRCUITPY_NVM = 0
 CIRCUITPY_DISPLAYIO = 0
 CIRCUITPY_FREQUENCYIO = 0
+
+INTERNAL_LIBM = 1