fails:RbConfig::CONFIG ['archdir'] returns the directory containing standard libraries C extensions
fails:RbConfig::CONFIG libdir/LIBRUBY_SO is the path to libruby and it exists if and only if ENABLE_SHARED
fails:RbConfig::CONFIG ['AR'] exists and can be executed
fails:RbConfig::CONFIG ['STRIP'] exists and can be executed
fails:RbConfig::CONFIG ['LIBRUBY'] is the same as LIBRUBY_SO if and only if ENABLE_SHARED
fails:RUBY_PLATFORM RUBY_PLATFORM contains a proper CPU architecture
fails:RUBY_PLATFORM RUBY_PLATFORM contains OS name
fails:RUBY_DESCRIPTION contains RUBY_PLATFORM
