Ensure linking bundled libraries

[kou]

If dependency libraries (czmq, libsodium and zeromq) are already installed in system and they exist in Ruby's library path, rbczmq uses headers of bundled libraries and shared objects of system libraries. Because link command generated by mkmf.rb uses $DEFLIBPATH | $LIBPATH as library search path. $DEFLIBPATH includes Ruby's library path. If dependency libraries already exist in Ruby's library path, they are used instead of bundled libraries.

It causes segmentation fault.

[kou]

See also:

• https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L2184
• https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L2256
• https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L2266
• https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L2514

[kou]

It seems that https://github.com/SciRuby/iruby/issues/70 is occurred by this problem.