Add standalone headers tests

[vsoulgard]

close #479

Added standalone compile tests for all public headers as new build target except src.hpp, because it already compiled separetely in other test target.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.17%. Comparing base (205080b) to head (6130d9c).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #517      +/-   ##
===========================================
- Coverage    99.17%   99.17%   -0.01%     
===========================================
  Files          146      146              
  Lines         7405     7400       -5     
===========================================
- Hits          7344     7339       -5     
  Misses          61       61              

see 1 file with indirect coverage changes

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[vsoulgard]

Dependencies are linked explicitly without linking with other targets to prevent masking missing includes.

However, it seems that all public headers were already self-contained.

[vsoulgard]

Thanks! I truly appreciate your patience and guidance.

But why CMake build should be an executable? I tried to make target OBJECT library previously, but it didn't link against dependencies and STATIC worked just fine.

And in B2 build we just trying to compile all files to see if there's compile errors without building an executable.

[vsoulgard]

CMake build also need to link Boost::pfr, because pfr.hpp includes <boost/pfr/config.hpp>

[anarthal]

Yes you are right about the executable comment, I was a bit picky. Static library should work fine too.

Pfr is supposed to be an optional dependency that you get only if you include that optional header, so it is expected to need the extra link libraries dependency.