bricks: fix broken build due to micropython/ subdirectory

The MicroPython build system expects MicroPython source code to be in
the top level directory, but in Pybricks it is not. Since we were adding
`micropython/` to the path, it was causing certain extra build options
to be missed, like the fix for micropython/micropython#6053.

Removing `micropython/` fixes this.

Fixes: pybricks/pybricks-micropython#40

bricks/ev3dev/Makefile

@@ -190,8 +190,15 @@ CFLAGS_MOD += -DPB_HAVE_LIBI2C=1
 LDFLAGS_MOD += -li2c
 endif
 
-# source files
-SRC_C = $(addprefix micropython/ports/unix/,\
+# Extra core MicroPython files
+
+# NB: Since we are using MicroPython's build system, files in the micropython/
+# directory have the micropython/ prefix excluded. It is very important to do
+# it that way since there is special handling of certain files that will break
+# if we don't do it this way. So we need to be very careful about name clashes
+# between the top level directory and the micropython/ subdirectory.
+
+SRC_C = $(addprefix ports/unix/,\
 	alloc.c \
 	coverage.c \
 	gccollect.c \
@@ -209,6 +216,13 @@ SRC_C = $(addprefix micropython/ports/unix/,\
 
 SRC_C += $(SRC_MOD)
 
+LIB_SRC_C = $(addprefix lib/,\
+	$(LIB_SRC_C_EXTRA) \
+	timeutils/timeutils.c \
+	utils/gchelper_generic.c \
+	utils/pyexec.c \
+	)
+
 # Pybricks port core source files
 PYBRICKS_SRC_C += \
 	ev3dev_mphal.c \
@@ -221,13 +235,6 @@ PYBRICKS_SRC_C += \
 	pbinit.c \
 	pbsmbus.c \
 
-LIB_SRC_C = $(addprefix micropython/lib/,\
-	$(LIB_SRC_C_EXTRA) \
-	timeutils/timeutils.c \
-	utils/gchelper_generic.c \
-	utils/pyexec.c \
-	)
-
 # Pybricks drivers and modules
 PYBRICKS_PYBRICKS_SRC_C = $(addprefix pybricks/,\
     pybricks.c \

bricks/nxt/Makefile

@@ -87,7 +87,15 @@ SRC_C = \
 	main.c \
 	systick.c \
 
-SRC_C += $(addprefix micropython/lib/,\
+# Extra core MicroPython files
+
+# NB: Since we are using MicroPython's build system, files in the micropython/
+# directory have the micropython/ prefix excluded. It is very important to do
+# it that way since there is special handling of certain files that will break
+# if we don't do it this way. So we need to be very careful about name clashes
+# between the top level directory and the micropython/ subdirectory.
+
+SRC_C += $(addprefix lib/,\
 	libc/string0.c \
 	mp-readline/readline.c \
 	utils/interrupt_char.c \
@@ -96,7 +104,7 @@ SRC_C += $(addprefix micropython/lib/,\
 	)
 
 SRC_S = \
-	micropython/lib/utils/gchelper_arm7tdmi.s \
+	lib/utils/gchelper_arm7tdmi.s \
 
 SRC_C_NXT := $(addprefix nxt-firmware-drivers/nxt/,\
 	aic.c \

bricks/stm32/stm32.mk

@@ -160,7 +160,15 @@ SRC_C = $(addprefix bricks/stm32/,\
 	uart_core.c \
 	)
 
-SRC_C += $(addprefix micropython/lib/,\
+# Extra core MicroPython files
+
+# NB: Since we are using MicroPython's build system, files in the micropython/
+# directory have the micropython/ prefix excluded. It is very important to do
+# it that way since there is special handling of certain files that will break
+# if we don't do it this way. So we need to be very careful about name clashes
+# between the top level directory and the micropython/ subdirectory.
+
+SRC_C += $(addprefix lib/,\
 	libc/string0.c \
 	mp-readline/readline.c \
 	utils/interrupt_char.c \
@@ -172,9 +180,9 @@ SRC_S = \
 	lib/pbio/platform/$(PBIO_PLATFORM)/startup.s \
 
 ifeq ($(PB_MCU_SERIES),F0)
-	SRC_S += micropython/lib/utils/gchelper_m0.s
+	SRC_S += lib/utils/gchelper_m0.s
 else
-	SRC_S += micropython/lib/utils/gchelper_m0.s
+	SRC_S += lib/utils/gchelper_m0.s
 endif
 
 # Pybricks modules
@@ -318,7 +326,7 @@ CONTIKI_SRC_C = $(addprefix lib/contiki-core/,\
 
 COPT += -DUSE_FULL_LL_DRIVER
 
-HAL_SRC_C = $(addprefix micropython/lib/stm32lib/STM32$(PB_MCU_SERIES)xx_HAL_Driver/Src/,\
+HAL_SRC_C = $(addprefix lib/stm32lib/STM32$(PB_MCU_SERIES)xx_HAL_Driver/Src/,\
 	stm32$(PB_MCU_SERIES_LCASE)xx_hal_adc_ex.c \
 	stm32$(PB_MCU_SERIES_LCASE)xx_hal_adc.c \
 	stm32$(PB_MCU_SERIES_LCASE)xx_hal_cortex.c \
@@ -453,7 +461,7 @@ LSM6DS3TR_C_SRC_C = lib/lsm6ds3tr_c_STdC/driver/lsm6ds3tr_c_reg.c
 
 # MicroPython math library
 
-SRC_LIBM = $(addprefix micropython/lib/libm/,\
+SRC_LIBM = $(addprefix lib/libm/,\
 	acoshf.c \
 	asinfacosf.c \
 	asinhf.c \