Update link to moved section (rust-lang#1282)

The section was removed in rust-lang#1030 and re-added in a different place in
2d42cf7.

Author: camelid

src/building/prerequisites.md

@@ -19,7 +19,7 @@ If building LLVM from source (the default), you'll need additional tools:
 Otherwise, you'll need LLVM installed and `llvm-config` in your path.
 See [this section for more info][sysllvm].
 
-[sysllvm]: ./suggested.md#skipping-llvm-build
+[sysllvm]: ./new-target.md#using-pre-built-llvm
 
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