Allow LLVM 11

[fxcoudert]

Homebrew now ships LLVM 11. This prevents us rebuilding arrow from source:

CMake Warning at cmake_modules/FindLLVMAlt.cmake:27 (find_package):
  Could not find a configuration file for package "LLVM" that is compatible
  with requested version "10".

[github-actions]

Thanks for opening a pull request!

Could you open an issue for this pull request on JIRA?
https://issues.apache.org/jira/browse/ARROW

Then could you also rename pull request title in the following format?

ARROW-${JIRA_ID}: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - How to contribute patches

[terencehonles]

It looks like there are more changes needed since the builder is still broken https://github.com/apache/arrow/pull/8492/checks?check_run_id=1279869182

[terencehonles]

Following up after the discussion in Homebrew/homebrew-core#63177 (comment) it looks like supporting LLVM 11 would be a good idea in the long term it is no longer a blocker to compiling arrow from source.

(I was able to fix this for the GitHub workflow by updating the cpp/Brewfile to only reference llvm@8 instead of llvm@8 and llvm)

[kou]

@fxcoudert Thanks for sending feedback from Homebrew!

I think that we need more changes to support LLVM 11 like we did by 6a1cdbc for LLVM 10.

It may be difficult for people who don't familiar with Apache Arrow build system. I'll take over this.

[pprudhvi]

@kou looks like this requires code changes, will we be able to build gandiva on centos with llvm 8?

[kou]

will we be able to build gandiva on centos with llvm 8?

I think so.

[kou]

#8521