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/reader/Cargo.toml

@@ -11,7 +11,7 @@ edition = "2018"
 
 [dependencies]
 cranelift-codegen = { path = "../cranelift-codegen", version = "0.41.0" }
-target-lexicon = "0.4.0"
+target-lexicon = "0.8.0"
 
 [badges]
 maintenance = { status = "experimental" }