Lives here now: https://github.com/mpv-player/mpv/blob/master/DOCS/compile-windows.md#native-compilation-with-msys2
👍
Oh jeez. I was starting the MSYS2 shell instead, serves me right for reading the instructions half asleep.
It works and compiles now, thanks.
Also, the
CC=gcc
bit in ./waf configure is important if you have MSYS2 gcc installed, since cc and gcc point to different compilers.