[meld] .gitignore: Add flatpak-builder folder

[Kai Willadsen <kaiw src gnome org>]

commit 29ab61651bf2e4c5db76d25971b89dbb35015ce7
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Wed Aug 1 18:03:29 2018 +1000

    .gitignore: Add flatpak-builder folder
    
    ...turns out it's very big and slow to recurse.

 .gitignore | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitignore b/.gitignore
index 860416d3..716cc1ee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@
 data/appdata.xml
 data/mime/meld.xml
 .cache/
+.flatpak-builder/
 .mypy_cache/
 build
 dist