Update test to get right tmp ruby folder
Update test to get right tmp ruby folder

The previous tests assumed that the temporary ruby folder created would
always be named `ruby`, but this is not always the case. Now, the folder
name is dynamically defined, so that different ruby versions will still
work.

pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler,pmq20/ruby-compiler