[rubygem-rdoc] Add BR: ruby(irb).

[Vít Ondruch]

commit e38cff9f908c884b259ac8d4dbd0144d9a8121b2
Author: Vít Ondruch <vondruch at redhat.com>
Date:   Tue Jul 8 13:56:14 2014 +0200

    Add BR: ruby(irb).

 rubygem-rdoc.spec |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/rubygem-rdoc.spec b/rubygem-rdoc.spec
index 4ef4860..3262c7e 100644
--- a/rubygem-rdoc.spec
+++ b/rubygem-rdoc.spec
@@ -17,6 +17,7 @@ BuildRequires: rubygem(json) => 1.4
 BuildRequires: rubygem(json) < 2
 # Execute Rake integration test cases.
 BuildRequires: rubygem(rake)
+BuildRequires: ruby(irb)
 BuildArch: noarch
 
 %description