Update apache-arrow for 2.0.0

[nealrichardson]

cf. r-windows/rtools-packages#160

[jeroen]

Is there any way to disable avx512 on unsupported compilers, so that we can build on osx 10.11?

I already tried to cheat by using the 10.13 libarrow binaries to build the R package on 10.11, however that results in a linking error Symbol not found: _os_unfair_lock_lock for something in libarrow_bundled_dependencies.a (probably jemalloc).

[nealrichardson]

Given https://github.com/apache/arrow/blob/master/cpp/cmake_modules/DefineOptions.cmake#L107-L122, it looks like we can set ARROW_RUNTIME_SIMD_LEVEL to something less--what would be appropriate, AVX2?

Presumably though if the compiler doesn't support AVX512 then we shouldn't be using it, so that suggests that the check for support (here I think? https://github.com/apache/arrow/blob/master/cpp/cmake_modules/SetupCxxFlags.cmake#L55) isn't doing the right thing for this compiler.

[jeroen]

Yeah let's try that, see what the CI says.

[jeroen]

Same error... looks like util/bpacking_avx512.cc is included unconditionally.

I think you need to condition that on ARROW_RUNTIME_SIMD_LEVEL as done here: https://github.com/apache/arrow/blob/44f3de2c2854a473d4ce184e02c4db83dffb805d/cpp/cmake_modules/SetupCxxFlags.cmake#L73

[nealrichardson]

You mean something like this? apache/arrow@699d702

[nealrichardson]

That appears to have allowed brew install to succeed

[jeroen]

Perfect, thanks!