mk: Use host llvm linkage paths, not target ones

We only build LLVM for the host architecture, not the target architecture, so
this was just a minor typo in the parameters uses.

Closes #19383
Fix the ordering of `unsafe` and `extern` in methods

This breaks code that looks like this:

    trait Foo {
        extern "C" unsafe fn foo();
    }

    impl Foo for Bar {
        extern "C" unsafe fn foo() { ... }
    }

Change such code to look like this:

    trait Foo {
        unsafe extern "C" fn foo();
    }

    impl Foo for Bar {
        unsafe extern "C" fn foo() { ... }
    }

Fixes #19398.

[breaking-change]
Fix typo in tests makefile
auto merge of #19418 : P1start/rust/unsafe-extern-trait, r=alexcrichton

Fixes #19398.
auto merge of #19425 : frewsxcv/rust/patch-1, r=steveklabnik

![](http://img2.wikia.nocookie.net/__cb20140809223829/disney/images/5/56/Darkwing_Duck_Poster_Promo.jpg)
auto merge of #19417 : alexcrichton/rust/issue-19383, r=huonw

We only build LLVM for the host architecture, not the target architecture, so
this was just a minor typo in the parameters uses.

Closes #19383