You can access the current cpu from builtin.cpu
const builtin = @import("builtin");
const cpu: std.Target.Cpu = builtin.cpu;
_ = cpu.features;
cpu.features is a list with all the features.
Use zig build-exe --show-builtin
or zig build-exe --show-builtin -target aarch64-linux-musl
to view all the builtin declarations with values for the current target.