[c++] Fix some build errors for Docker

[johnkerl]

Issue and/or context: Found in Docker builds for cloud deploys, using 1.15.4. Compling fine on our CI though. See #3154.

Changes:

Notes for Reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.31%. Comparing base (4e92187) to head (5d89309).
Report is 1 commits behind head on release-1.15.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.15    #3620      +/-   ##
================================================
+ Coverage         86.26%   86.31%   +0.04%     
================================================
  Files                55       55              
  Lines              6378     6378              
================================================
+ Hits               5502     5505       +3     
+ Misses              876      873       -3     

Flag	Coverage Δ
python	86.31% <ø> (+0.04%)	⬆️

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Components	Coverage Δ
python_api	86.31% <ø> (+0.04%)	⬆️
libtiledbsoma	∅ <ø> (∅)