build llvm with systemz backend enabled, and link to related libraries

[japaric]

when building rust against system llvm

closes#36077

r? @alexcrichton

[rust-highfive]

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[japaric]

link to related libraries when building rust against system llvm

this fixes the travis builds. We could add a build slave that tests building rust against system llvm to avoid these in the future

[japaric]

build slave

I meant bors. Travis doesn't block PRs.

[japaric]

cc @TimNN

[alexcrichton]

Thanks @japaric! I'll wait to r+ until travis is green

[alexcrichton]

@bors: r+

[bors]

📌 Commit 15d8dfb has been approved by alexcrichton

[bors]

⌛ Testing commit 15d8dfb with merge 06ab76a...

[bors]

💔 Test failed - auto-mac-64-opt-rustbuild

[arielb1]

@bors retry

[arielb1]

@bors p=1

[bors]

⌛ Testing commit 15d8dfb with merge 77d2cd2...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-no-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-no-mir, auto-win-msvc-64-opt-rustbuild
Approved by: alexcrichton
Pushing 77d2cd2 to master...