Auto merge of rust-lang#48736 - alexcrichton:fix-rust-src, r=3

Include stdsimd in rust-src component

Closes rust-lang#48734

Author: bors

src/bootstrap/dist.rs

@@ -810,6 +810,7 @@ impl Step for Src {
             "src/libterm",
             "src/jemalloc",
             "src/libprofiler_builtins",
+            "src/stdsimd",
         ];
         let std_src_dirs_exclude = [
             "src/libcompiler_builtins/compiler-rt/test",