Improve RUBY_GC_LIBRARY
Instead of passing the full GC SO file name to RUBY_GC_LIBRARY, we now only need to pass the GC name.
For example, before we needed to pass RUBY_GC_LIBRARY=librubygc.default.so but now we only need to pass RUBY_GC_LIBRARY=default.
RUBY_GC_LIBRARY=librubygc.default.so
RUBY_GC_LIBRARY=default
Improve RUBY_GC_LIBRARY
Instead of passing the full GC SO file name to RUBY_GC_LIBRARY, we now
only need to pass the GC name.
For example, before we needed to pass
RUBY_GC_LIBRARY=librubygc.default.sobut now we only need to pass
RUBY_GC_LIBRARY=default.