macOS also requires avrdude

docs/getting_started_build_tools.md

@@ -53,6 +53,7 @@ If you're using [homebrew,](http://brew.sh/) you can use the following commands:
     brew install avr-gcc
     brew install dfu-programmer
     brew install gcc-arm-none-eabi
+    brew install avrdude
 
 This is the recommended method. If you don't have homebrew, [install it!](http://brew.sh/) It's very much worth it for anyone who works in the command line. Note that the `make` and `make install` portion during the homebrew installation of avr-libc can take over 20 minutes and exhibit high CPU usage.