py/mkrules.mk: Use $(CPP) not $(CC) -E for preprocessor rule.
@@ -53,7 +53,7 @@ vpath %.c . $(TOP) $(USER_C_MODULES)
$(BUILD)/%.pp: %.c
$(ECHO) "PreProcess $<"
- $(Q)$(CC) $(CFLAGS) -E -Wp,-C,-dD,-dI -o $@ $<
+ $(Q)$(CPP) $(CFLAGS) -Wp,-C,-dD,-dI -o $@ $<
# The following rule uses | to create an order only prerequisite. Order only
# prerequisites only get built if they don't exist. They don't cause timestamp
