Enable rustdoc to document safe wasm intrinsics

This commit fixes an issue not found during #84988 where rustdoc is used
to document cross-platform intrinsics but it was requiring that
functions which use `#[target_feature]` are `unsafe` erroneously, even
if they're WebAssembly specific. Rustdoc today, for example, already has
a special case where it enables annotations like
`#[target_feature(enable = "simd128")]` on platforms other than
WebAssembly. The purpose of this commit is to relax the "require all
`#[target_feature]` functions are `unsafe`" requirement for all targets
whenever rustdoc is running, enabling all targets to fully document
other targets, such as WebAssembly, where intrinsics functions aren't
always `unsafe`.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/test/rustdoc-ui/wasm-safe.rs b/src/test/rustdoc-ui/wasm-safe.rs
new file mode 100644
index 00000000000..80b15ace0ee
--- /dev/null
+++ b/src/test/rustdoc-ui/wasm-safe.rs
@@ -0,0 +1,7 @@
+// check-pass
+
+#![feature(wasm_target_feature)]
+
+#[cfg(any(target_arch = "wasm32", doc))]
+#[target_feature(enable = "simd128")]
+pub fn foo() {}