use CMake 3.8.2 in CMake CI jobs

[grisumbras]

No description provided.

[cppalliance-bot]

An automated preview of the documentation is available at https://1110.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

[cppalliance-bot]

An automated preview of the documentation is available at https://1110.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1110/pullrequest.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.71%. Comparing base (9dd59bc) to head (a6fbf10).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1110   +/-   ##
========================================
  Coverage    93.71%   93.71%           
========================================
  Files           91       91           
  Lines         9156     9156           
========================================
  Hits          8581     8581           
  Misses         575      575           

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[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1110/pullrequest.html

[cppalliance-bot]

An automated preview of the documentation is available at https://1110.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1110/pullrequest.html