build: Make bash-completion support optional

Whether we install bash-completion support currently depends on whether
the corresponding pkg-config dependency is found.

Turning this into a feature option keeps that behavior by default, but
also allows to explicitly enable or disable the support.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1072

subprojects/extensions-tool/meson.build

@@ -33,7 +33,7 @@ json_dep = dependency('json-glib-1.0')
 
 cc = meson.get_compiler('c')
 
-bash_completion = dependency('bash-completion', required: false)
+bash_completion = dependency('bash-completion', required: get_option('bash_completion'))
 
 subdir('src')
 

subprojects/extensions-tool/meson_options.txt

@@ -5,6 +5,12 @@ option('man',
   yield: true,
 )
 
+option('bash_completion',
+  type: 'feature',
+  value: 'auto',
+  description: 'Install bash completion support',
+)
+
 option('package_name',
   type: 'string',
   description: 'The gettext domain name when used as a subproject'