equate libdir with the directory that libjulia was loaded from

contrib/julia-config.jl

@@ -12,8 +12,7 @@ function imagePath()
 end
 
 function libDir()
- @unix_only return match(r"(.*)(sys.ji)",imagePath()).captures[1];
- @windows_only return Base.JULIA_HOME;
+ return abspath(dirname(Sys.dlpath("libjulia")));
 end
 
 function includeDir()