The >=dev-perl/File-MimeInfo-0.170.0 ebuilds declare a dependency on virtual/perl-Module-Build. However, that's not enough: Building with older versions of that module fails ("Module::Build version 0.40 required--this is only version 0.3901 at ./Build line 41."). Therefore, the ebuild should explicitly state a dependency on >=virtual/perl-Module-Build-0.400.0.
It is already depend on it.
No, it doesn't. Did you even read the bug description?
*** This bug has been marked as a duplicate of bug 502192 ***