move -flto to board.mk

current board that doesn work with flto is spresense and mimxrt10xx (due
to xip image_vector_table is optimized out).

hw/bsp/stm32f303disco/board.mk

@@ -1,13 +1,14 @@
 CFLAGS += \
-	-DHSE_VALUE=8000000 \
-	-DSTM32F303xC \
-	-mthumb \
-	-mabi=aapcs \
-	-mcpu=cortex-m4 \
-	-mfloat-abi=hard \
-	-mfpu=fpv4-sp-d16 \
-	-nostdlib -nostartfiles \
-	-DCFG_TUSB_MCU=OPT_MCU_STM32F3
+  -flto \
+  -mthumb \
+  -mabi=aapcs \
+  -mcpu=cortex-m4 \
+  -mfloat-abi=hard \
+  -mfpu=fpv4-sp-d16 \
+  -nostdlib -nostartfiles \
+  -DSTM32F303xC \
+  -DHSE_VALUE=8000000 \
+  -DCFG_TUSB_MCU=OPT_MCU_STM32F3
 
 # mcu driver cause following warnings
 CFLAGS += -Wno-error=unused-parameter
@@ -19,21 +20,21 @@ ST_CMSIS = hw/mcu/st/st_driver/CMSIS/Device/ST/STM32F3xx
 LD_FILE = hw/bsp/$(BOARD)/STM32F303VCTx_FLASH.ld
 
 SRC_C += \
-	$(ST_CMSIS)/Source/Templates/system_stm32f3xx.c \
-	$(ST_HAL_DRIVER)/Src/stm32f3xx_hal.c \
-	$(ST_HAL_DRIVER)/Src/stm32f3xx_hal_cortex.c \
-	$(ST_HAL_DRIVER)/Src/stm32f3xx_hal_rcc.c \
-	$(ST_HAL_DRIVER)/Src/stm32f3xx_hal_rcc_ex.c \
-	$(ST_HAL_DRIVER)/Src/stm32f3xx_hal_gpio.c
+  $(ST_CMSIS)/Source/Templates/system_stm32f3xx.c \
+  $(ST_HAL_DRIVER)/Src/stm32f3xx_hal.c \
+  $(ST_HAL_DRIVER)/Src/stm32f3xx_hal_cortex.c \
+  $(ST_HAL_DRIVER)/Src/stm32f3xx_hal_rcc.c \
+  $(ST_HAL_DRIVER)/Src/stm32f3xx_hal_rcc_ex.c \
+  $(ST_HAL_DRIVER)/Src/stm32f3xx_hal_gpio.c
 
 SRC_S += \
-	$(ST_CMSIS)/Source/Templates/gcc/startup_stm32f303xc.s
+  $(ST_CMSIS)/Source/Templates/gcc/startup_stm32f303xc.s
 
 INC += \
-	$(TOP)/hw/mcu/st/st_driver/CMSIS/Include \
-	$(TOP)/$(ST_CMSIS)/Include \
-	$(TOP)/$(ST_HAL_DRIVER)/Inc \
-	$(TOP)/hw/bsp/$(BOARD)
+  $(TOP)/hw/mcu/st/st_driver/CMSIS/Include \
+  $(TOP)/$(ST_CMSIS)/Include \
+  $(TOP)/$(ST_HAL_DRIVER)/Inc \
+  $(TOP)/hw/bsp/$(BOARD)
 
 # For TinyUSB port source
 VENDOR = st