[gnome-shell] build: Use fixed gettext domain for non-subproject extension-tool builds

[Florian Müllner <fmuellner src gnome org>]

commit 8a89e22e8ea293cc03e741635d0e75625081ece5
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Mar 5 14:28:21 2020 +0100

    build: Use fixed gettext domain for non-subproject extension-tool builds
    
    Clarify how the option is supposed to be used by
     - ignoring it for non-subproject builds
     - enforcing that it is set for subproject builds
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1072

 subprojects/extensions-tool/meson.build       | 9 ++++++++-
 subprojects/extensions-tool/meson_options.txt | 3 +--
 2 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/subprojects/extensions-tool/meson.build b/subprojects/extensions-tool/meson.build
index 0cee112348..ffaf49bd32 100644
--- a/subprojects/extensions-tool/meson.build
+++ b/subprojects/extensions-tool/meson.build
@@ -9,7 +9,14 @@ gio_req = '>= 2.56.0'
 gnome = import('gnome')
 i18n  = import('i18n')
 
-package_name = get_option('package_name')
+if meson.is_subproject()
+  package_name = get_option('package_name')
+  assert(package_name != '',
+    'package_name must be specified for subproject builds')
+else
+  package_name = meson.project_name()
+endif
+
 package_version = meson.project_version()
 prefix = get_option('prefix')
 
diff --git a/subprojects/extensions-tool/meson_options.txt b/subprojects/extensions-tool/meson_options.txt
index d106bf8896..9963d8ff7e 100644
--- a/subprojects/extensions-tool/meson_options.txt
+++ b/subprojects/extensions-tool/meson_options.txt
@@ -7,6 +7,5 @@ option('man',
 
 option('package_name',
   type: 'string',
-  value: 'gnome-extensions-tool',
-  description: 'The gettext domain name'
+  description: 'The gettext domain name when used as a subproject'
 )