[gnome-flashback] shell: fix distcheck error

[Alberts Muktupāvels <muktupavels src gnome org>]

commit fce8040601abfe5000e91a34f873a59599fcfcdd
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Mar 30 23:03:12 2015 +0300

    shell: fix distcheck error

 gnome-flashback/libshell/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gnome-flashback/libshell/Makefile.am b/gnome-flashback/libshell/Makefile.am
index 3743cc7..03e9061 100644
--- a/gnome-flashback/libshell/Makefile.am
+++ b/gnome-flashback/libshell/Makefile.am
@@ -3,6 +3,7 @@ noinst_LTLIBRARIES = \
 
 AM_CPPFLAGS = \
        $(SHELL_CFLAGS) \
+       -I$(srcdir)/../../gnome-flashback \
        -I$(top_builddir)/gnome-flashback \
        -I$(top_builddir)/gnome-flashback/libshell