CPU feature checking - common back-end

 The packages in the isa-support family probe for microprocessor Instruction
 Set Architecture features such as SSE3. By refusing to install on machines
 lacking a required feature, they allow ISA requirements to be handled in
 terms of package dependencies.
 .
 This package provides the feature-probing infrastructure. To assert a CPU
 requirement, other packages can pre-depend on one of the individual
 feature-specific packages:
 .
 sse2-support, sse3-support, sse4.2-support, altivec-support, neon-support,
 armv6-support, armv7-support, armv8-support, vfp-support, vfpv2-support,
 vfpv3-support