Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

…arations

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Improves error handling in STEPattributeList operator[] - return an
error attribute and set error state rather than trying to rely on
crashing via a NULL deference.  That's undefined behavior, so it
was not guaranteed - this requires the calling code to check the
return, but is *much* cleaner.

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

…p-supertype-andor

Fix test_exppp_supertype_andor CMake version inconsistency

…ling modernizations to do here...

Various fixes for building with new compilers, update Github workflows for new BRL-CAD compilation setup, one behavior correction - rather than trying to use a NULL pointer deference to crash in an error case (bad practice and undefined behavior anyway) return an error attribute calling applications can deal with gracefully.

Merges pull request stepcode#466 from starseeker/buildfixes

Clean up stray SC_BUILD_STATIC_LIBS and SC_BUILD_TYPE variables.
Install schema libs
Fix linking when doing static builds

Complete CMake variable migration, fix schema library installation