don't build tests in CMake by default

[grisumbras]

Fix #1005

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1006/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1006/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1006/pullrequest.html

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.41%. Comparing base (1f6f1a2) to head (3d02a24).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1006   +/-   ##
========================================
  Coverage    93.41%   93.41%           
========================================
  Files           87       87           
  Lines         8547     8547           
========================================
  Hits          7984     7984           
  Misses         563      563           

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[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1006/pullrequest.html