[gtkmm-documentation] Update build/.gitignore

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 0d1d4630869fecfd82551991c0f8c0683b5af215
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Sep 7 07:57:03 2017 +0200

    Update build/.gitignore

 build/.gitignore |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/build/.gitignore b/build/.gitignore
index 2d993ed..c7f3933 100644
--- a/build/.gitignore
+++ b/build/.gitignore
@@ -1,3 +1,4 @@
+/compile
 /compile-binding.am
 /config.*
 /depcomp