[gnome-software] build: Install gnome-software-install-appstream in the correct dir

[Joaquim Manuel Pereira Rocha <jrocha src gnome org>]

commit bad3f3c35efdc6e20580811709e19294e2622f60
Author: Joaquim Rocha <jrocha endlessm com>
Date:   Wed Sep 20 11:54:16 2017 +0200

    build: Install gnome-software-install-appstream in the correct dir
    
    It needs to be installed in the libexecdir that's given as an option.

 plugins/external-appstream/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plugins/external-appstream/meson.build b/plugins/external-appstream/meson.build
index 6bc4510..ea5d3d2 100644
--- a/plugins/external-appstream/meson.build
+++ b/plugins/external-appstream/meson.build
@@ -9,7 +9,7 @@ executable(
   dependencies : [gio_unix, appstream_glib],
   c_args : cargs,
   install : true,
-  install_dir : 'libexec'
+  install_dir : get_option('libexecdir')
 )
 
 shared_module(