upgrade to target-lexicon 0.8.0

* the target-lexicon crate no longer has or needs the std feature
  in cargo, so we can delete all default-features=false, any mentions
  of its std feature, and the nostd configs in many lib.rs files
* the representation of arm architectures has changed, so some case
  statements needed refactoring

cranelift/wasm/Cargo.toml

@@ -23,7 +23,7 @@ serde = { version = "1.0.94", features = ["derive"], optional = true }
 
 [dev-dependencies]
 wabt = "0.9.1"
-target-lexicon = "0.4.0"
+target-lexicon = "0.8.0"
 
 [features]
 default = ["std"]

cranelift/wasm/src/lib.rs

@@ -28,7 +28,6 @@
     )
 )]
 #![no_std]
-#![cfg_attr(not(feature = "std"), feature(alloc))]
 
 #[cfg(not(feature = "std"))]
 #[macro_use]