ci: Enable msys2 ci in cirrus

Install msys2 in a proper way refer to:
 https://github.com/cirruslabs/cirrus-ci-docs/issues/699
The https://wiki.qemu.org/Hosts/W32#Native_builds_with_MSYS2 need to be updated.
There is no need of --cross-prefix, open mingw64.exe instead of msys2.exe then
we don't need the --cross-prefix, besides we use environment variable settings:
    MSYS: winsymlinks:nativestrict
    MSYSTEM: MINGW64
    CHERE_INVOKING: 1
to opening mingw64 native shell.

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200915121318.247-25-luoyonggang@gmail.com>
[thuth: Add --target-list-exclude to speed it up a little bit, and
        add capstone package to avoid build failure with internal capstone]
Signed-off-by: Thomas Huth <thuth@redhat.com>

.cirrus.yml

@@ -63,3 +63,66 @@ macos_xcode_task:
                    --enable-werror --cc=clang || { cat config.log; exit 1; }
     - gmake -j$(sysctl -n hw.ncpu)
     - gmake check
+
+windows_msys2_task:
+  windows_container:
+    image: cirrusci/windowsservercore:cmake
+    os_version: 2019
+    cpu: 8
+    memory: 8G
+  env:
+    MSYS: winsymlinks:nativestrict
+    MSYSTEM: MINGW64
+    CHERE_INVOKING: 1
+  printenv_script:
+    - C:\tools\msys64\usr\bin\bash.exe -lc 'printenv'
+  install_script:
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd /c/tools &&
+        curl -O http://repo.msys2.org/msys/x86_64/msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd /c/tools &&
+        curl -O http://repo.msys2.org/msys/x86_64/msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz.sig"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd /c/tools &&
+        pacman -U --noconfirm msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "pacman --noconfirm -Sy"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "pacman --noconfirm -S --needed
+        bash pacman pacman-mirrors msys2-runtime"
+    - taskkill /F /IM gpg-agent.exe
+    - C:\tools\msys64\usr\bin\bash.exe -lc "pacman --noconfirm -Su"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "pacman --noconfirm -S --needed
+        base-devel
+        git
+        mingw-w64-x86_64-python
+        mingw-w64-x86_64-python-setuptools
+        mingw-w64-x86_64-toolchain
+        mingw-w64-x86_64-capstone
+        mingw-w64-x86_64-SDL2
+        mingw-w64-x86_64-SDL2_image
+        mingw-w64-x86_64-gtk3
+        mingw-w64-x86_64-glib2
+        mingw-w64-x86_64-ninja
+        mingw-w64-x86_64-make
+        mingw-w64-x86_64-lzo2
+        mingw-w64-x86_64-zstd
+        mingw-w64-x86_64-libjpeg-turbo
+        mingw-w64-x86_64-pixman
+        mingw-w64-x86_64-libgcrypt
+        mingw-w64-x86_64-libpng
+        mingw-w64-x86_64-libssh
+        mingw-w64-x86_64-libxml2
+        mingw-w64-x86_64-snappy
+        mingw-w64-x86_64-libusb
+        mingw-w64-x86_64-usbredir
+        mingw-w64-x86_64-libtasn1
+        mingw-w64-x86_64-nettle
+        mingw-w64-x86_64-cyrus-sasl
+        mingw-w64-x86_64-curl
+        mingw-w64-x86_64-gnutls
+        mingw-w64-x86_64-zstd"
+  script:
+    - C:\tools\msys64\usr\bin\bash.exe -lc "mkdir build"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd build && ../configure
+      --python=python3 --ninja=ninja
+      --target-list-exclude=i386-softmmu,arm-softmmu,ppc-softmmu,mips-softmmu"
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd build && make -j$NUMBER_OF_PROCESSORS"
+  test_script:
+    - C:\tools\msys64\usr\bin\bash.exe -lc "cd build && make V=1 check"