.cirrus.yml: Change winsymlinks to 'native'

At present winsymlinks is set to 'nativestrict', and its behavior is:

  a) if native symlinks are enabled and <target> exists, creates
     <destination> as a native Windows symlink;
  b) else if native symlinks are not enabled or if <target> does
     not exist, 'ln -s' fails.

This causes the following error message was seen during the configure:

  "ln: failed to create symbolic link
  'x86_64-softmmu/qemu-system-x86_64.exe': No such file or directory"

Change winsymlinks to 'native' whose behavior is most similar to the
behavior of 'ln -s' on *nix, that is:

  a) if native symlinks are enabled, and whether <target> exists
     or not, creates <destination> as a native Windows symlink;
  b) else if native symlinks are not enabled, and whether <target>
     exists or not, 'ln -s' creates as a Windows shortcut file.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Yonggang Luo <luoyonggang@gmail.com>
Message-Id: <20220719161230.766063-1-bmeng.cn@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220725140520.515340-5-alex.bennee@linaro.org>