Add support for building organic via nix.

Cargo.toml

@@ -1,5 +1,4 @@
 # cargo-features = ["profile-rustflags"]
-cargo-features = ["codegen-backend"]
 
 [package]
 name = "organic"
@@ -104,9 +103,5 @@ inherits = "release"
 lto = true
 strip = true
 
-[profile.dev]
-codegen-backend = "cranelift"
-
 [profile.dev.package."*"]
-codegen-backend = "llvm"
 opt-level = 3