[gedit] build: avoid a global variable for gtkdocdir

[Sébastien Wilmet <swilmet src gnome org>]

commit ff446ccb5560952bad5b613ea28d4c8338534787
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sat Mar 14 15:15:30 2020 +0100

    build: avoid a global variable for gtkdocdir
    
    To keep related things grouped together.

 docs/reference/meson.build | 2 ++
 meson.build                | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/docs/reference/meson.build b/docs/reference/meson.build
index edac1919c..abf5ed7c0 100644
--- a/docs/reference/meson.build
+++ b/docs/reference/meson.build
@@ -76,6 +76,8 @@ libgedit_reference_mkdb_args = [
   '--name-space=gedit',
 ]
 
+gtkdocdir = join_paths(get_option('prefix'), get_option('datadir'), 'gtk-doc')
+
 libgedit_reference_fixxref_args = [
   '--html-dir=@0@'.format(join_paths(gtkdocdir, 'html', package_string)),
   '--extra-dir=@0@'.format(glib_docpath),
diff --git a/meson.build b/meson.build
index 29718df69..21e1173d1 100644
--- a/meson.build
+++ b/meson.build
@@ -31,7 +31,6 @@ pkglibdir = join_paths(libdir, meson.project_name())
 pkgdatadir = join_paths(datadir, meson.project_name())
 
 glibdir = join_paths(datadir, 'glib-2.0')
-gtkdocdir = join_paths(datadir, 'gtk-doc')
 vapidir = join_paths(datadir, 'vala', 'vapi')
 
 # Subprojects