target: fix destabilising target-spec-json

compiler/rustc_target/src/spec/mod.rs

@@ -3352,6 +3352,9 @@ fn load_file(
 
                 Err(format!("could not find specification for target {target_tuple:?}"))
             }
+            TargetTuple::TargetJson { ref contents, .. } if !unstable_options => {
+                Err("custom targets are unstable and require `-Zunstable-options`".to_string())
+            }
             TargetTuple::TargetJson { ref contents, .. } => Target::from_json(contents),
         }
     }

tests/run-make/rust-lld-custom-target/rmake.rs

@@ -15,7 +15,11 @@ fn main() {
     // Compile to a custom target spec with rust-lld enabled by default. We'll check that by asking
     // the linker to display its version number with a link-arg.
     assert_rustc_uses_lld(
-        rustc().crate_type("cdylib").target("custom-target.json").input("lib.rs"),
+        rustc()
+            .crate_type("cdylib")
+            .target("custom-target.json")
+            .arg("-Zunstable-options")
+            .input("lib.rs"),
     );
 
     // But it can also be disabled via linker features.

tests/run-make/rustdoc-target-spec-json-path/rmake.rs

@@ -5,8 +5,14 @@
 
 fn main() {
     let out_dir = "rustdoc-target-spec-json-path";
-    rustc().crate_type("lib").input("dummy_core.rs").target("target.json").run();
+    rustc()
+        .arg("-Zunstable-options")
+        .crate_type("lib")
+        .input("dummy_core.rs")
+        .target("target.json")
+        .run();
     rustdoc()
+        .arg("-Zunstable-options")
         .input("my_crate.rs")
         .out_dir(out_dir)
         .library_search_path(cwd())

tests/run-make/target-specs/rmake.rs

@@ -20,13 +20,20 @@ fn main() {
         .target("my-incomplete-platform.json")
         .run_fail()
         .assert_stderr_contains("missing field `llvm-target`");
-    let test_platform = rustc()
+    let _ = rustc()
         .input("foo.rs")
         .target("my-x86_64-unknown-linux-gnu-platform")
         .crate_type("lib")
         .emit("asm")
         .run_fail()
         .assert_stderr_contains("custom targets are unstable and require `-Zunstable-options`");
+    let _ = rustc()
+        .input("foo.rs")
+        .target("my-awesome-platform.json")
+        .crate_type("lib")
+        .emit("asm")
+        .run_fail()
+        .assert_stderr_contains("custom targets are unstable and require `-Zunstable-options`");
     rustc()
         .arg("-Zunstable-options")
         .env("RUST_TARGET_PATH", ".")

tests/ui/check-cfg/values-target-json.rs

@@ -4,7 +4,8 @@
 //@ check-pass
 //@ no-auto-check-cfg
 //@ needs-llvm-components: x86
-//@ compile-flags: --crate-type=lib --check-cfg=cfg() --target={{src-base}}/check-cfg/my-awesome-platform.json
+//@ compile-flags: --crate-type=lib --check-cfg=cfg()
+//@ compile-flags: -Zunstable-options --target={{src-base}}/check-cfg/my-awesome-platform.json
 //@ ignore-backends: gcc
 
 #![feature(lang_items, no_core, auto_traits, rustc_attrs)]