[gedit] build: add option to disable installing the externaltools plugin

[Sébastien Wilmet <swilmet src gnome org>]

commit 5e58ee3c2332001d30337c182b6e5e43a54a8f0e
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Fri May 1 04:12:11 2020 +0200

    build: add option to disable installing the externaltools plugin
    
    The externaltools plugin doesn't work on Windows, there is an error when
    loading it, it cannot import fcntl (which is specific to Unix).
    
    So, be able to not install the plugin.
    
    Maybe there is a way to make that plugin work on Windows, but I'm far
    from an expert in Python, so contributions welcome.

 meson_options.txt   | 2 ++
 plugins/meson.build | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/meson_options.txt b/meson_options.txt
index baaf67aa9..4e842d1ea 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -20,3 +20,5 @@ option(
   type: 'boolean', value: true,
   description: 'Build user documentation'
 )
+
+option('plugin_externaltools', type: 'boolean', value: true)
diff --git a/plugins/meson.build b/plugins/meson.build
index fbdf98265..50bc5d393 100644
--- a/plugins/meson.build
+++ b/plugins/meson.build
@@ -16,7 +16,6 @@ msgfmt_plugin_cmd = [
 ]
 
 subdir('docinfo')
-subdir('externaltools')
 subdir('filebrowser')
 subdir('modelines')
 subdir('pythonconsole')
@@ -26,3 +25,7 @@ subdir('snippets')
 subdir('sort')
 subdir('spell')
 subdir('time')
+
+if get_option('plugin_externaltools')
+  subdir('externaltools')
+endif