compiler: Switch to rustc_abi in hir_pretty, lint_defs, and mir_build

Completely abandon usage of rustc_target in these crates, as
they need no special knowledge of rustc's target tuples.

compiler/rustc_hir_pretty/src/lib.rs

@@ -9,6 +9,7 @@
 use std::cell::Cell;
 use std::vec;
 
+use rustc_abi::ExternAbi;
 use rustc_ast::util::parser::{self, AssocOp, Fixity};
 use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
 use rustc_ast_pretty::pp::{self, Breaks};
@@ -20,7 +21,6 @@ use rustc_hir::{
 use rustc_span::FileName;
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_target::spec::abi::Abi;
 use {rustc_ast as ast, rustc_hir as hir};
 
 pub fn id_to_string(map: &dyn rustc_hir::intravisit::Map<'_>, hir_id: HirId) -> String {
@@ -2240,7 +2240,7 @@ impl<'a> State<'a> {
 
     fn print_ty_fn(
         &mut self,
-        abi: Abi,
+        abi: ExternAbi,
         safety: hir::Safety,
         decl: &hir::FnDecl<'_>,
         name: Option<Symbol>,
@@ -2276,7 +2276,7 @@ impl<'a> State<'a> {
 
         self.print_safety(header.safety);
 
-        if header.abi != Abi::Rust {
+        if header.abi != ExternAbi::Rust {
             self.word_nbsp("extern");
             self.word_nbsp(header.abi.to_string());
         }