Use HIDE_SYMBOLS_BY_DEFAULT

[scpeters]

🎉 New feature

Part of testing gazebosim/gz-cmake#392.

Summary

Test it

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #130 (9c7bde7) into main (88d429b) will increase coverage by 0.46%.
Report is 3 commits behind head on main.
The diff coverage is n/a.

❗ Current head 9c7bde7 differs from pull request most recent head d49c544. Consider uploading reports for the commit d49c544 to get more accurate results

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
+ Coverage   98.26%   98.72%   +0.46%     
==========================================
  Files          23       23              
  Lines         748      785      +37     
==========================================
+ Hits          735      775      +40     
+ Misses         13       10       -3     

Files	Coverage Δ
loader/src/cmd/gz.cc	96.15% <ø> (+7.26%)	⬆️

... and 10 files with indirect coverage changes