State all supported targets for rustc-link-arg.

src/doc/src/reference/unstable.md

@@ -26,10 +26,10 @@ Some unstable features will require you to specify the `cargo-features` key in
 The `-Z extra-link-arg` flag makes the following two instructions available
 in build scripts:
 
-* [`cargo:rustc-link-arg-bins=FLAG`](#rustc-link-arg-bins) — Passes custom
-  flags to a linker for bin crates.
-* [`cargo:rustc-link-arg=FLAG`](#rustc-link-arg) — Passes custom
-  flags to a linker for all supported crates.
+* [`cargo:rustc-link-arg-bins=FLAG`](#rustc-link-arg-bins) – Passes custom
+  flags to a linker for binaries.
+* [`cargo:rustc-link-arg=FLAG`](#rustc-link-arg) – Passes custom flags to a
+  linker for benchmarks, binaries, `cdylib` crates, examples, and tests.
 
 <a id="rustc-link-arg-bins"></a>
 #### `cargo:rustc-link-arg-bins=FLAG`
@@ -45,9 +45,10 @@ to set a linker script or other linker options.
 #### `cargo:rustc-link-arg=FLAG`
 
 The `rustc-link-arg` instruction tells Cargo to pass the [`-C link-arg=FLAG`
-option][link-arg] to the compiler, but only when building a supported target
-(currently a binary or `cdylib` library). Its usage is highly platform
-specific. It is useful to set the shared library version or linker script.
+option][link-arg] to the compiler, but only when building supported targets
+(benchmarks, binaries, `cdylib` crates, examples, and tests). Its usage is
+highly platform specific. It is useful to set the shared library version or
+linker script.
 
 [link-arg]: ../../rustc/codegen-options/index.md#link-arg