[gnome-builder] build: set fallback for older meson versions

[Christian Hergert <chergert src gnome org>]

commit 734135520f255ac041cb3b073e72689a7aca4baa
Author: Christian Hergert <chergert redhat com>
Date:   Sun Jun 18 15:41:57 2017 -0700

    build: set fallback for older meson versions
    
    Older Meson versions do not have the default value specified
    for the fallback parameter.

 libide/meson.build |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/libide/meson.build b/libide/meson.build
index a0b816e..920aad9 100644
--- a/libide/meson.build
+++ b/libide/meson.build
@@ -16,6 +16,7 @@ libide_version_h = configure_file(
   configuration: version_data)
 
 vcs_tag(
+     fallback: meson.project_version(),
         input: 'ide-build-ident.h.in',
        output: 'ide-build-ident.h',
       install: true,