Leonardo,
I did the re-install as below, then searched the build log as suggested (also below). Mine looks almost identical to yours, unless I am missing something. But the results are the same. I am really stumped.
Grateful for any more suggestions - or diagnostics that I could run to check out the build and install.
After that, did you use rvm use to tell it that you wante to use the ruby you've just compiled?
Fred