waf编译器取代make编译器

根据ardupilot/BUILD.md

Ardupilot is gradually moving from the make-based build system to
[Waf](https://waf.io/). The instructions below should be enough for you to
build Ardupilot, but you can also read more about the build system in the
[Waf Book](https://waf.io/book/). //ArduPilot逐渐由make编译转向Waf编译，具体指导见https://waf.io/book/

Waf should always be called from the ardupilot's root directory. Differently
from the make-based build, with Waf there's a configure step to choose the
board to be used (default is `sitl`). //waf编译命令应在"ardupilot/"根目录下，与make编译不同，而且waf第一步是configure命令，选择硬件板类型，默认硬件板是sitl。

硬件Pixracer，固件ArduCopter，waf编译命令如下：
cd ardupilot
./waf configure --board fmuv4
./waf copter

waf命令

waf [commands] [options]
commands:

options: