Msys2 have three way of running (or three shells if you wish): MSYS, MINGW32, MINGW64. You should run MINGW32 or MINGW64.
As you can see in my post (you did read my post with long log, right?) I used MINGW32.
Maybe you run MINGW64? Then you should install x64-bit fdk-aac library instead of x32. To do so run
pacman -Syu --needed mingw-w64-x86_64-fdk-aac