I am not aware of a method to "svn:ignore the svn:ignore", I don't think it's possible.
The svn:ignore
property has very likely been altered by another programmer, who has already checked that change in - so your working copy now remains in a conflicted state. You should see a file called dir_conflicts.prej
describing the conflict in detail - which you will need to manually resolve. To quote the SVN book:
You should examine the contents of this file so you can decide how to resolve the conflict. Until the conflict is resolved, you will see a C in the second column of svn status output for that object, and attempts to commit your local modifications will fail.
...and:
To resolve property conflicts, simply ensure that the conflicting properties contain the values that they should, and then use the svn resolve --accept=working command to alert Subversion that you have manually resolved the problem.