增加了一些编译优化，增加了log使用文档，新增部分user_lib功能

Makefile

@@ -199,7 +199,7 @@ FPU = -mfpu=fpv4-sp-d16
 FLOAT-ABI = -mfloat-abi=hard
 
 # mcu
-MCU = $(CPU) -mthumb $(FPU) $(FLOAT-ABI)
+MCU = $(CPU) -mthumb -mthumb-interwork $(FPU) $(FLOAT-ABI)
 
 # macros for gcc
 # AS defines
@@ -211,7 +211,9 @@ C_DEFS =  \
 -DSTM32F407xx \
 -DARM_MATH_CM4 \
 -DARM_MATH_MATRIX_CHECK \
--DARM_MATH_ROUNDING 
+-DARM_MATH_ROUNDING \
+-DARM_MATH_LOOPUNROLL \
+-DISABLEFLOAT16
 
 # AS includes
 AS_INCLUDES =  \
@@ -277,7 +279,7 @@ C_INCLUDES =  \
 # compile gcc flags
 ASFLAGS = $(MCU) $(AS_DEFS) $(AS_INCLUDES) $(OPT) -fdata-sections -ffunction-sections
 
-CFLAGS += $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -fdata-sections -ffunction-sections
+CFLAGS += $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -fdata-sections -ffunction-sections -fmessage-length=0
 
 ifeq ($(DEBUG), 1)
 CFLAGS += -g -gdwarf-2
@@ -299,7 +301,7 @@ LIBS = -lc -lm -lnosys  \
 -l:libarm_cortexM4lf_math.a
 LIBDIR =  \
 -LMiddlewares/ST/ARM/DSP/Lib
-LDFLAGS = $(MCU) -specs=nano.specs -T$(LDSCRIPT) $(LIBDIR) $(LIBS) -Wl,-Map=$(BUILD_DIR)/$(TARGET).map,--cref -Wl,--gc-sections
+LDFLAGS = $(MCU) -specs=nano.specs -T$(LDSCRIPT) $(LIBDIR) $(LIBS) -Wl,-Map=$(BUILD_DIR)/$(TARGET).map,--cref -Wl,--gc-sections -flto
 
 # default action: build all
 all: $(BUILD_DIR)/$(TARGET).elf $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin
@@ -339,7 +341,7 @@ $(BUILD_DIR):
 # clean up
 #######################################
 clean:
-	rd /s/q $(BUILD_DIR)
+	rd $(BUILD_DIR) /s/q
 
 
 #######################################