Support for embedding arbitrary string to Linux kernel command line

Issue #45

This commit adds supports for adding arbitrary strings to the Linux
kernel commandline.

A user can set a shell env variable EXTRA_CMDLINE_LINUX with a
string that needs to be embedded in the kernel commandline.

Exmaple usage provided in machine/kvm_x86_64/machine.make.

NOTE: Currently, we're only supporting x86 arch.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Alpha_Networks_SNQ6070_320F:Add machine support to SNQ6070_320F

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Prevent stripping of /lib/modules/ external kernel modules

Solving:
<module name>: module has no symbols (stripped?)
modprobe: '<module ko file>': invalid module format

Tests:
modprobe of external module

Signed-off-by: Doron Tsur <doront@mellanox.com>