[gcab] build-sys: fix installing the includes

[Marc-André Lureau <malureau src gnome org>]

commit 150c330de1e65036250a2788a51245e37c7de0f7
Author: Timo Gurr <timo gurr gmail com>
Date:   Thu Feb 1 16:16:21 2018 +0100

    build-sys: fix installing the includes
    
    https://bugzilla.gnome.org/show_bug.cgi?id=793388

 libgcab/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgcab/meson.build b/libgcab/meson.build
index 6ff8801..f939617 100644
--- a/libgcab/meson.build
+++ b/libgcab/meson.build
@@ -9,7 +9,7 @@ enums = gnome.mkenums(
   c_template : 'gcab-enums.c.etemplate',
   h_template : 'gcab-enums.h.etemplate',
   install_header : true,
-  install_dir : 'include/libgcab-1.0/libgcab',
+  install_dir : join_paths(get_option('includedir'), 'libgcab-1.0/libgcab'),
   symbol_prefix : 'gcab',
   identifier_prefix : 'GCab',
 )