Disable sse4_2

kallikrates/iktinos lack this, they're opteron 6128s. 
2 jobs for master in 141 minutes and 25 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #170425195
lineage-builder triggered
build

01:50:17

 
  Sign
passed #170425196
signing-proxy triggered
sign

00:31:07