Single quotes like -prom-env 'nvramrc=cafec0de 4000 l!' in the arguments
are not removed in the Windows environment before it is passed to the
QEMU executable. Such argument causes a failure in the QEMU prom-env
option parser codes.

Change to use double quotes which works fine on all platforms.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220824094029.1634519-46-bmeng.cn@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>