Use configure_file() to configure version only

[trivialfis]

@hcho3 This keeps most of your clean up, but added back the intrin detection code in order to avoid writing build_config.h in include directory. After this, only version upgrade can change that file.

[hcho3]

@trivialfis If the goal is to avoid polluting the include directory, can we apply something like dmlc/dmlc-core#551?

[hcho3]

After this, only version upgrade can change that file

We should formally enforce this, rather than making it an unwritten convention. Perhaps create a separate config step just for the version (version_config.h)? The reason is that we may want to configure more things in the future.

Let me think of something and get back to you.

[trivialfis]

@hcho3 Good point.

[hcho3]

Let me try incorporating ideas from dmlc/dmlc-core#551 and dmlc/dmlc-core#566 and get back to you.

[trivialfis]

@hcho3 I removed the build_config.h completely and moved those macros into base.h since that's where most of our macros defined, also previously base.h includes build_config.h.

I also added a version_config.h that does only configuring version information.

[hcho3]

I see your point about the "include only what you need" principle. At best, you'd get an error like "XGBOOST_VER_MAJOR symbol not found" and you'll be reminded to include xgboost/version_config.h.

[hcho3]

Note: Should we need to use configure_file() for other things in the future, we should try to apply lessons learned from dmlc/dmlc-core#551 and dmlc/dmlc-core#566.

[trivialfis]

@hcho3 Agreed. until we can remove those makefiles, your method works better.

[hcho3]

Will merge once tests pass.

[codecov-io]

Codecov Report

Merging #4974 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4974   +/-   ##
=======================================
  Coverage   71.82%   71.82%           
=======================================
  Files          11       11           
  Lines        2300     2300           
=======================================
  Hits         1652     1652           
  Misses        648      648

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[trivialfis]

@hcho3 Thanks for the help. ;-)