x86_64: Use the x86-64 level for purgatory

The compiler may be configured by default to use a newer
microarchitecture level such as x86-64-v3. Set purgatory to compile
using the baseline x86-64 level since the environment isn't set up
correctly to use SSE and AVX instructions.  At the same time, be a bit
paranoid and add some additional flags to ensure that the compiler
doesn't use any such instructions.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Simon Horman <horms@kernel.org>
1 file changed