This is what happened when I tried the make file
C:\esp_iot_sdk_v0.9.1\examples\at>make
CC driver/uart.c
CC user/at_baseCmd.c
CC user/at_cmd.c
CC user/at_ipCmd.c
CC user/at_port.c
CC user/at_wifiCmd.c
CC user/user_main.c
AR build/esp8266_at_app.a
LD build/esp8266_at.out
FW firmware/0x00000.bin
esptool -eo build/esp8266_at.out -bo firmware/0
s .rodata -bc -ec
make: esptool: Command not found
make: *** [firmware/0x00000.bin] Error 127