Quick start on a Linux build host:
# Install Meson and a recent build of MinGW-w64, then:
$ meson --cross cross-mingw-32.txt _build32
$ ninja -C _build32
$ meson --cross cross-mingw-64.txt _build64
$ ninja -C _build64
Building on MSYS2 is also possible; consult Meson documentation for details.
Additional documentation will be forthcoming.