Update dev guide to fix clang linking issue on arm

[finnroblin]

Description

The current DEVELOPER_GUIDE.md M-series instructions did not work for me or @MrFlap. These updated instructions use gcc/g++ instead of clang to build and link the external kNN libraries. The project builds for me (m3 chip) and Andrew (m2 chip).

Issues Resolved

Resolves linking issues with m-series macbook chips when building kNN locally.

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed as per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[shatejas]

/opt/homebrew/opt/llvm/bin/clang works for me. Can we keep both? you can add a note saying change to

in case of error: [Add the error] change to
export CC=gcc
export CXX=g++

[finnroblin]

Sure and let me ask Andrew what his error was -- I think they were different.

[finnroblin]

Pasting entire error trace here so that people can find it in search. Both of us had linking errors with clang:

<after running make>
77%] Building CXX object CMakeFiles/opensearchknn_faiss.dir/src/faiss_wrapper.cpp.o
[ 79%] Building CXX object CMakeFiles/opensearchknn_faiss.dir/src/faiss_util.cpp.o
<FAILS HERE> [ 79%] Linking CXX shared library release/libopensearchknn_faiss.jnilib

Here's the trace:

Homebrew clang version 18.1.7
Target: arm64-apple-darwin23.5.0
Thread model: posix
InstalledDir: /opt/homebrew/opt/llvm/bin
 "/usr/bin/ld" -demangle -lto_library /opt/homebrew/Cellar/llvm/18.1.7/lib/libLTO.dylib -dynamic -dylib -arch arm64 -dylib_install_name @rpath/libopensearchknn_faiss.jnilib -platform_version macos 14.0.0 14.4 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -mllvm -enable-linkonceodr-outlining -o release/libopensearchknn_faiss.jnilib -headerpad_max_install_names CMakeFiles/opensearchknn_faiss.dir/src/org_opensearch_knn_jni_FaissService.cpp.o CMakeFiles/opensearchknn_faiss.dir/src/faiss_wrapper.cpp.o CMakeFiles/opensearchknn_faiss.dir/src/faiss_util.cpp.o -rpath /Users/finnrobl/Code/k-NN/jni/release external/faiss/faiss/libfaiss.a release/libopensearchknn_util.jnilib -framework Accelerate -lm -ldl /opt/homebrew/opt/llvm/lib/libomp.dylib -lc++ -lSystem /opt/homebrew/Cellar/llvm/18.1.7/lib/clang/18/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture arm64:
  "std::exception_ptr::__from_native_exception_pointer(void*)", referenced from:
      std::__1::promise<bool>::~promise() in libfaiss.a[77](WorkerThread.cpp.o)
  "___cxa_init_primary_exception", referenced from:
      std::__1::promise<bool>::~promise() in libfaiss.a[77](WorkerThread.cpp.o)
ld: symbol(s) not found for architecture arm64
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [release/libopensearchknn_faiss.jnilib] Error 1
make[1]: *** [CMakeFiles/opensearchknn_faiss.dir/all] Error 2
make: *** [all] Error 2

[ryanbogan]

What is the difference between these lines?

[finnroblin]

Nothing intentional. I may have deleted a trailing whitespace but I'm not sure what triggered the diff.

[ryanbogan]

Can you add a changelog entry? Otherwise looks good to me!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.06%. Comparing base (9023604) to head (eb14858).
Report is 7 commits behind head on main.

❗ Current head eb14858 differs from pull request most recent head 535092e

Please upload reports for the commit 535092e to get more accurate results.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1746      +/-   ##
============================================
- Coverage     85.09%   85.06%   -0.04%     
- Complexity     1473     1486      +13     
============================================
  Files           178      178              
  Lines          5937     6051     +114     
  Branches        607      632      +25     
============================================
+ Hits           5052     5147      +95     
- Misses          633      644      +11     
- Partials        252      260       +8     

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