[gnome-software] build: Add option to disable the API reference

[Emmanuele Bassi <ebassi src gnome org>]

commit 923e899add0b5ae89e9f3e90b3044294efd0fc15
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Aug 28 23:54:15 2017 +0100

    build: Add option to disable the API reference
    
    The GNOME Continuous integration system does not build the
    documentation, to avoid the DocBook dependencies, and to avoid excessive
    build times.

 doc/meson.build   |    4 +++-
 meson_options.txt |    1 +
 2 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/doc/meson.build b/doc/meson.build
index dc2bb41..7827d92 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -1 +1,3 @@
-subdir('api')
+if get_option('enable-gtk-doc')
+  subdir('api')
+endif
diff --git a/meson_options.txt b/meson_options.txt
index f723c30..ddfd585 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -19,3 +19,4 @@ option('enable-gudev', type : 'boolean', value : true, description : 'enable GUd
 option('enable-snap', type : 'boolean', value : false, description : 'enable Snap support')
 option('enable-external-appstream', type : 'boolean', value : false, description : 'enable external 
AppStream support')
 option('enable-valgrind', type : 'boolean', value : true, description : 'enable Valgrind debugging 
integration')
+option('enable-gtk-doc', type : 'boolean', value : true, description : 'enable API reference')