Remove -Z strip.

It was stabilized as `-C strip` in November 2021. The unstable option
was kept around as a temporary measure to ease the transition. Two years
is more than enough!

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1033,7 +1033,7 @@ fn link_natively<'a>(
  SplitDebuginfo::Packed => link_dwarf_object(sess, codegen_results, out_filename),
  }
 
- let strip = strip_value(sess);
+ let strip = sess.opts.cg.strip;
 
  if sess.target.is_like_osx {
  match (strip, crate_type) {
@@ -1070,14 +1070,6 @@ fn link_natively<'a>(
  Ok(())
 }
 
-// Temporarily support both -Z strip and -C strip
-fn strip_value(sess: &Session) -> Strip {
- match (sess.opts.unstable_opts.strip, sess.opts.cg.strip) {
- (s, Strip::None) => s,
- (_, s) => s,
- }
-}
-
 fn strip_symbols_with_external_utility<'a>(
  sess: &'a Session,
  util: &str,
@@ -2370,7 +2362,7 @@ fn add_order_independent_options(
  );
 
  // Pass debuginfo, NatVis debugger visualizers and strip flags down to the linker.
- cmd.debuginfo(strip_value(sess), &natvis_visualizers);
+ cmd.debuginfo(sess.opts.cg.strip, &natvis_visualizers);
 
  // We want to prevent the compiler from accidentally leaking in any system libraries,
  // so by default we tell linkers not to link to any default libraries.

compiler/rustc_session/src/options.rs

@@ -1841,8 +1841,6 @@ written to standard error output)"),
  "prefer dynamic linking to static linking for staticlibs (default: no)"),
  strict_init_checks: bool = (false, parse_bool, [TRACKED],
  "control if mem::uninitialized and mem::zeroed panic on more UB"),
- strip: Strip = (Strip::None, parse_strip, [UNTRACKED],
- "tell the linker which information to strip (`none` (default), `debuginfo` or `symbols`)"),
  #[rustc_lint_opt_deny_field_access("use `Session::teach` instead of this field")]
  teach: bool = (false, parse_bool, [TRACKED],
  "show extended diagnostic help (default: no)"),