Choose ECLIPSE_INSTALLER based on (OSTYPE,MACHINE)

For the time being the following configurations are supported:
* (GNU/Linux, i686)
* (GNU/Linux, x86_64)

Signed-off-by: Gianpaolo Macario <gianpaolo_macario@mentor.com>
Configure for box hashicorp/precise32

Rationale: One of my old Linux boxes runs Ubuntu 64-bit
but has no VT-x support, therefore only 32-bit guest OSs
are supported by VirtualBox.

Signed-off-by: Gianpaolo Macario <gianpaolo_macario@mentor.com>