libpqxx: Improve test

[jviotti]

It seems that this libpqxx static library is somehow broken. Some basic programs, like the one currently provided in the formula, work fine, but certain components of the library seem to fail.

This PR is extending the current test to hopefully surface the error I'm seeing.

See jtv/libpqxx#739

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[jviotti]

I'm not well versed with Homebrew, but sounds like this formula should be updated to use CMake instead of Autotools, so it exports a CMake config script for find_package instead of only a pkg-config integration.

[chenrui333]

I'm not well versed with Homebrew, but sounds like this formula should be updated to use CMake instead of Autotools, so it exports a CMake config script for find_package instead of only a pkg-config integration.

The only concern would be it would broke the dependencies which are using pc file (does cmake build generate pc config in the upstream)

[jviotti]

@chenrui333 Looks like their CMake integration still generates the .pc file: https://github.com/jtv/libpqxx/blob/master/src/CMakeLists.txt#L88-L91

[jviotti]

Hm, looks like the GitHub Actions tests are indeed passing. Weird. Can somebody check the example reproducible app I provided in the upstream bug report: jtv/libpqxx#739? Here is the direct link: https://github.com/jviotti/pqxx-test

That definitely fails for me, but only with the Homebrew formula. Building it from source actually works for me. I was expecting it to fail on CI here.