tests: Provide G_TEST_SRCDIR, G_TEST_BUILDDIR to lint scripts

These scripts use $(readlink -f) to guess their own path if necessary,
but macOS readlink doesn't support the -f option, and POSIX doesn't
guarantee that readlink even exists.

Resolves: https://gitlab.gnome.org/GNOME/glib/-/issues/3289
Fixes: d7601f7e "Incorporate some lint checks into `meson test`"
Signed-off-by: Simon McVittie <smcv@collabora.com>

tests/meson.build

@@ -1,6 +1,10 @@
 # Copyright 2024 Collabora Ltd.
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
+test_env = environment()
+test_env.set('G_TEST_SRCDIR', meson.current_source_dir())
+test_env.set('G_TEST_BUILDDIR', meson.current_build_dir())
+
 lint_scripts = [
   'black.sh',
   'flake8.sh',
@@ -12,7 +16,7 @@ if have_bash
   foreach test_name : lint_scripts
     test(
       test_name, files(test_name),
-      env : common_test_env,
+      env : test_env,
       suite : ['lint', 'no-valgrind'],
       protocol : 'tap',
     )
@@ -23,7 +27,7 @@ test(
   'check-missing-install-tag.py',
   python,
   args : ['-B', files('check-missing-install-tag.py')],
-  env : common_test_env,
+  env : test_env,
   suite : ['lint', 'no-valgrind'],
   protocol : 'tap',
 )