build system option to allow CPU optimizations?

[Ricardo Wurmus]

Hi Guix,

currently we patch source code and build systems to ensure that no 
special instructions are used that would not be portable, 
e.g. AVX2, SSE4.1 etc.  What do you think of adding a build system 
option that would allow users to restore these optimizations?

The build phases that patch out these features would have to check 
for that build system option, much like they check the TESTS? 
option before attempting to run tests.

What do you think?

--
Ricardo