Support passing cflags/cxxflags/ldflags to LLVM build

[petrhosek]

This may be needed with some host compilers.

[rust-highfive]

r? @alexcrichton

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[alexcrichton]

@bors: r+ rollup

👍

[bors]

📌 Commit cbe1d2bc4097711acb8248c62ec6ccfea8791677 has been approved by alexcrichton

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout llvm-flags (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self llvm-flags --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging src/bootstrap/native.rs
Auto-merging src/bootstrap/configure.py
Auto-merging src/bootstrap/config.rs
CONFLICT (content): Merge conflict in src/bootstrap/config.rs
Auto-merging config.toml.example
CONFLICT (content): Merge conflict in config.toml.example
Automatic merge failed; fix conflicts and then commit the result.

[cramertj]

@bors r=alexcrichton rollup

[bors]

📌 Commit c663272 has been approved by alexcrichton

[Centril]

@bors rollup-

[bors]

⌛ Testing commit c663272 with merge 286ac62...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: alexcrichton
Pushing 286ac62 to master...