Meson decided to crossbuild for Windows as soon as
meson.is_cross_build() returned true. This made non-Windows crossbuilds
fail.
Instead, add an explicit option "crossbuild_windows".
Fixes <https://github.com/Genymobile/scrcpy/issues/165>.
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.
Romain Vimont