* Avoid making all warnings into errors
* Extra optimizations via COPT should be overwritable 

--- mpy-cross/Makefile.orig	2026-04-06 13:12:49 UTC
+++ mpy-cross/Makefile
@@ -6,6 +6,10 @@ QSTR_DEFS = qstrdefsport.h
 # qstr definitions (must come before including py.mk)
 QSTR_DEFS = qstrdefsport.h
 
+# Enable compressed ROM text so genhdr/compressed.data.h is generated before
+# compilation when the unix port passes -DMICROPY_ROM_TEXT_COMPRESSION=1.
+MICROPY_ROM_TEXT_COMPRESSION = 1
+
 # OS name, for simple autoconfig
 UNAME_S := $(shell uname -s)
 
@@ -17,7 +21,7 @@ INC += -I$(TOP)
 INC += -I$(TOP)
 
 # compiler settings
-CWARN = -Wall -Werror
+CWARN = -Wall
 CWARN += -Wextra -Wno-unused-parameter -Wpointer-arith
 CFLAGS += $(INC) $(CWARN) -std=gnu99 $(COPT) $(CFLAGS_EXTRA)
 CFLAGS += -fdata-sections -ffunction-sections -fno-asynchronous-unwind-tables
@@ -25,9 +29,9 @@ CFLAGS += -g
 # Debugging/Optimization
 ifdef DEBUG
 CFLAGS += -g
-COPT = -O0
+COPT ?= -O0
 else
-COPT = -Os #-DNDEBUG
+COPT ?= -Os #-DNDEBUG
 endif
 
 # On OSX, 'gcc' is a symlink to clang unless a real gcc is installed.
@@ -58,5 +62,11 @@ OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 
 OBJ = $(PY_CORE_O)
 OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
+
+# mpy-cross is a host-only cross-compiler with no threading or frozen modules.
+# Undefine unix port flags that bleed in via the combined sub-make CFLAGS so
+# the resulting binary does not reference unimplemented symbols.
+CFLAGS += -UMICROPY_PY_THREAD -UMICROPY_QSTR_EXTRA_POOL \
+	-UMICROPY_MODULE_FROZEN_MPY -UMICROPY_MODULE_FROZEN_STR
 
 include $(TOP)/py/mkrules.mk