tests: Actually test libregress by specifying the LD_LIBRARY_PATH
Looking at the tests log will give your:
65/65 gitypelibtest OK 0.02 s
--- command ---
GI_TYPELIB_PATH='/builds/GNOME/gobject-introspection/_build/gir:/builds/GNOME/gobject-introspection/_build/tests:/builds/GNOME/gobject-introspection/_build/tests/scanner' /builds/GNOME/gobject-introspection/_build/tests/repository/gitypelibtest
--- stderr ---
** (process:5367): WARNING **: 15:46:55.373: Failed to load shared library 'libregress-1.0.so' referenced by the typelib: libregress-1.0.so: cannot open shared object file: No such file or directory
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This should probably be a failure but at least the .so is found now