site: add more alignment values for at-spi2-core

x86 and x86_64 values were added in 8c46ec. The x86-64 values were missing an
entry, add MIPS and PowerPC values from myself in qemu, and ARM values from
Martin Jansa.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
runqemu: when tunctl can't be found, say what package builds it

If runqemu is used without actually building any qemu images (i.e. you
downloaded the images) it's likely that qemu-helper-native hasn't been built.
Instead of just saying what command can't be found, tell the user how to solve
their problem.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>