Appveyor: Download 7zip instead of using the one appveyor provides
Appveyor: Download 7zip instead of using the one appveyor provides

For some reason appveyor sometimes fails to use the preinstalled 7zip.

Signed-off-by: Dan <2f664a27dbc3ee2034ed9e950b3808890cb5416a@analog.com>

analogdevicesinc/Pixelpulse2,analogdevicesinc/Pixelpulse2,analogdevicesinc/Pixelpulse2