"std" builds need to enable the "std" feature in cranelift-codegen.

Author: sunfishcode

cranelift-preopt/Cargo.toml

@@ -18,6 +18,11 @@ cranelift-entity = { path = "../cranelift-entity", version = "0.45.0" }
 # cranelift currently supports.
 # rustc_apfloat = { version = "0.1.2", default-features = false }
 
+[features]
+default = ["std"]
+std = ["cranelift-codegen/std"]
+core = ["cranelift-codegen/core"]
+
 [badges]
 maintenance = { status = "experimental" }
 travis-ci = { repository = "CraneStation/cranelift" }