Rollup merge of #130034 - alexcrichton:fix-some-wasm-component-ld-comments, r=onur-ozkan

 Fix enabling wasm-component-ld to match other tools

It was [pointed out recently][comment] that enabling `wasm-component-ld` as a host tool is different from other host tools. This commit refactors the logic to match by deduplicating selection of when to build other tools and then using the same logic for `wasm-component-ld`.

While here I also fixed a typo pointed out in rust-lang/rust#126967 (review)

[comment]: rust-lang/rust#127866 (comment)

Author: workingjubilee