stf_lib CTest regression

[StanSofomoDev]

This pull request introduces a regression target for unit testing STF_LIB using CTest. The regression tests can be executed with the following commands:

mkdir -p release/
cd release/
cmake .. -DCMAKE_BUILD_TYPE=Release
make -j32 regress
cd ..

Currently, these tests serve as a stub and do not cover the STF_LIB extensively (only one basic STFWriter test was added).

[klingaard]

This is great! And appreciated. One thing this doesn't really test is making sure the file written contains the expected information written. Suggest adding an stf_reader after the close and making sure the file read matches what was written.

[StanSofomoDev]

This is great! And appreciated. One thing this doesn't really test is making sure the file written contains the expected information written. Suggest adding an stf_reader after the close and making sure the file read matches what was written.

Written file contents are tested by diff comparison to golden file that is included in the test directory.

[StanSofomoDev]

@bdutro, @klingaard, main purpose for this PR is to add CTest environment to the stf_lib, proper tests that would cover components of the stf_lib can be added in the future.

[bdutro]

This all looks good. Could you go ahead and add a make regress call to https://github.com/sparcians/stf_lib/blob/master/.github/workflows/ubuntu-build.yml so it runs for PRs?

[bdutro]

LGTM