[qt] add comment to justify use of --vendor=qt4

[Rex Dieter]

commit a4ee2e1f924056385e775aeed4099b5a583c75d1
Author: Rex Dieter <rdieter at math.unl.edu>
Date:   Tue Apr 23 15:39:37 2013 -0500

    add comment to justify use of --vendor=qt4

 qt.spec |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/qt.spec b/qt.spec
index c5038b0..4f52e50 100644
--- a/qt.spec
+++ b/qt.spec
@@ -647,7 +647,7 @@ rsync -aR \
   %{buildroot}%{_prefix}/
 %endif
 
-# Add desktop file(s)
+# Add desktop files, --vendor=qt4 helps avoid possible conflicts with qt3/qt5
 desktop-file-install \
   --dir=%{buildroot}%{_datadir}/applications \
   --vendor="qt4" \