qga: gspawn() console helper to Windows guest agent msi build

qga: gspawn() console helper to Windows guest agent msi build

This helper, gspawn-win64-helper-console.exe for 64-bit and
gspawn-win32-helper-console.exe for 32-bit environment,
is needed for gspawn() mingw implementation, used by guest-exec command.

Without these files guest-exec command on Windows will not
work with "file not found" diagnostic message.

Signed-off-by: Yuri Pudgorodskiy <yur@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>