On Windows, an application is either console or gui, it cannot be both.
Scrcpy should be both: it outputs important information to console, but
we still want to be able to ignore the console and launch it without a
visible cmd.exe window.
Therefore, build two binaries:
- scrcpy.exe
- scrcpy-noconsole.exe
Build the Windows binary from mingw on Linux, using the official
prebuilt binaries for ffmpeg, SDL2 and adb.
MSYS2 and all its packaged dll are not necessary anymore.