Hi there,

I feel like I've tried everything under the sun to install xgboost on my mac (mohave), but I'm still running into dead ends.

Some things I've tried:
#4477
When I run the step

$ cmake ..

I get this error:

`-- The CXX compiler identification is GNU 5.5.0
-- The C compiler identification is GNU 5.5.0
-- Checking whether CXX compiler has -isysroot
-- Checking whether CXX compiler has -isysroot - yes
-- Checking whether CXX compiler supports OSX deployment target flag
-- Checking whether CXX compiler supports OSX deployment target flag - yes
-- Check for working CXX compiler: /usr/local/bin/g++-5
-- Check for working CXX compiler: /usr/local/bin/g++-5 -- broken
CMake Error at /usr/local/Cellar/cmake/3.15.4/share/cmake/Modules/CMakeTestCXXCompiler.cmake:53 (message):
The C++ compiler

"/usr/local/bin/g++-5"

is not able to compile a simple test program.

It fails with the following output:

Change Dir: /Users/camp426/xgboost/build/CMakeFiles/CMakeTmp

Run Build Command(s):/Users/camp426/anaconda3/bin/make cmTC_55296/fast && /Users/camp426/anaconda3/bin/make -f CMakeFiles/cmTC_55296.dir/build.make CMakeFiles/cmTC_55296.dir/build
make[1]: Entering directory '/Users/camp426/xgboost/build/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_55296.dir/testCXXCompiler.cxx.o
/usr/local/bin/g++-5    -march=core2 -mtune=haswell -mssse3 -ftree-vectorize -fPIC -fPIE -fstack-protector-strong -O2 -pipe -stdlib=libc++ -fvisibility-inlines-hidden -std=c++14 -fmessage-length=0  -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -mmacosx-version-min=10.14   -o CMakeFiles/cmTC_55296.dir/testCXXCompiler.cxx.o -c /Users/camp426/xgboost/build/CMakeFiles/CMakeTmp/testCXXCompiler.cxx
g++-5: error: unrecognized command line option '-stdlib=libc++'
make[1]: *** [CMakeFiles/cmTC_55296.dir/build.make:66: CMakeFiles/cmTC_55296.dir/testCXXCompiler.cxx.o] Error 1
make[1]: Leaving directory '/Users/camp426/xgboost/build/CMakeFiles/CMakeTmp'
make: *** [Makefile:121: cmTC_55296/fast] Error 2

CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt:2 (project)

-- Configuring incomplete, errors occurred!
See also "/Users/camp426/xgboost/build/CMakeFiles/CMakeOutput.log".
See also "/Users/camp426/xgboost/build/CMakeFiles/CMakeError.log".`

I have homebrew, I've updated homebrew, I've tried installing xgboost (using both pip and pip3) with gcc5, gcc8, and gcc9.2 (newest version), none work. I get the same error:

Command "python setup.py egg_info" failed with error code 1

Which I see by the multiple issues that I found googling that this is a known issue.

I'm in dead-end land. Help please.