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)"),