meson: Put test setup behind a feature option

This should allow the following cases:

- In case of "auto" (the default): meson will check if the necessary
  binaries are installed (such as `dbus-run-session`) on the system and
  fall back.
- In case of "enabled": meson will require the necessary binaries to be
  installed
- In case of "disabled": meson will not try to mark this as the default
  test setup.

The first case was already the default, however, some systems have a
preconfigured test setup which they'd like to use instead. Allow them to
disable the default test setup in that case.

Fixes: https://gitlab.gnome.org/GNOME/libsecret/-/issues/101

meson.build

@@ -102,7 +102,7 @@ test_env = environment()
 test_env.set('abs_top_builddir', meson.build_root())
 
 # Most tests require a D-Bus session, so try to wrap automatically with dbus-run-session
-dbus_run_session = find_program('dbus-run-session', required: false)
+dbus_run_session = find_program('dbus-run-session', required: get_option('test_setup'))
 if dbus_run_session.found()
   add_test_setup('dbus',
     exe_wrapper: dbus_run_session,

meson_options.txt

@@ -61,3 +61,8 @@ option('pam',
   description: 'Build PAM module',
 )
 
+option('test_setup',
+  type: 'feature',
+  value: 'auto',
+  description: 'Automatically setup a test environment when running tests',
+)