[gdm/wip/no-check] meson: don't require libcheck

[Ray Strode <halfline src gnome org>]

commit bf4aa1be9f493632e3dbcd6ae56a2cc97ea6d29a
Author: Ray Strode <rstrode redhat com>
Date:   Fri May 1 11:23:14 2020 -0400

    meson: don't require libcheck
    
    The runtime doesn't have it, so don't require it.

 meson.build | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 23d66f59..b0f46e5b 100644
--- a/meson.build
+++ b/meson.build
@@ -256,7 +256,9 @@ subdir('libgdm')
 subdir('utils')
 subdir('pam_gdm')
 subdir('po')
-subdir('tests')
+if libcheck_dep.found()
+  subdir('tests')
+endif
 if xdmcp_dep.found()
   subdir('chooser')
 endif