rustdoc book: Move --test-builder(--wrapper)? docs to unstable section.

src/doc/rustdoc/src/command-line-arguments.md

@@ -447,32 +447,3 @@ This flag is **deprecated** and **has no effect**.
 Rustdoc only supports Rust source code and Markdown input formats. If the
 file ends in `.md` or `.markdown`, `rustdoc` treats it as a Markdown file.
 Otherwise, it assumes that the input file is Rust.
-
-## `--test-builder`: `rustc`-like program to build tests
-
-Using this flag looks like this:
-
-```bash
-$ rustdoc --test-builder /path/to/rustc src/lib.rs
-```
-
-Rustdoc will use the provided program to compile tests instead of the default `rustc` program from
-the sysroot.
-
-## `--test-builder-wrapper`: wrap calls to the test builder
-
-Using this flag looks like this:
-
-```bash
-$ rustdoc --test-builder-wrapper /path/to/rustc-wrapper src/lib.rs
-$ rustdoc \
-    --test-builder-wrapper rustc-wrapper1 \
-    --test-builder-wrapper rustc-wrapper2 \
-    --test-builder rustc \
-    src/lib.rs
-```
-
-Similar to cargo `build.rustc-wrapper` option, this flag takes a `rustc` wrapper program.
-The first argument to the program will be the test builder program.
-
-This flag can be passed multiple times to nest wrappers.

src/doc/rustdoc/src/unstable-features.md

@@ -627,3 +627,36 @@ add the `--scrape-tests` flag.
 
 This flag enables the generation of links in the source code pages which allow the reader
 to jump to a type definition.
+
+### `--test-builder`: `rustc`-like program to build tests
+
+ * Tracking issue: [#102981](https://github.com/rust-lang/rust/issues/102981)
+
+Using this flag looks like this:
+
+```bash
+$ rustdoc --test-builder /path/to/rustc src/lib.rs
+```
+
+Rustdoc will use the provided program to compile tests instead of the default `rustc` program from
+the sysroot.
+
+### `--test-builder-wrapper`: wrap calls to the test builder
+
+ * Tracking issue: [#102981](https://github.com/rust-lang/rust/issues/102981)
+
+Using this flag looks like this:
+
+```bash
+$ rustdoc -Zunstable-options --test-builder-wrapper /path/to/rustc-wrapper src/lib.rs
+$ rustdoc -Zunstable-options \
+    --test-builder-wrapper rustc-wrapper1 \
+    --test-builder-wrapper rustc-wrapper2 \
+    --test-builder rustc \
+    src/lib.rs
+```
+
+Similar to cargo `build.rustc-wrapper` option, this flag takes a `rustc` wrapper program.
+The first argument to the program will be the test builder program.
+
+This flag can be passed multiple times to nest wrappers.