[tepl] build: add comment

[Sébastien Wilmet <swilmet src gnome org>]

commit ed8b1cdfde9a4d0037634e3819310bef49179b98
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon May 4 16:04:22 2020 +0200

    build: add comment
    
    See commit d2b330866ed0f38f528bbada939df94254b8e2e9 (by Xavier Claessens).

 tepl/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/tepl/meson.build b/tepl/meson.build
index c5acad2..64ee726 100644
--- a/tepl/meson.build
+++ b/tepl/meson.build
@@ -185,5 +185,6 @@ GNOME.generate_gir(
     tepl_public_c_files,
     tepl_enum_types
   ],
+  # Support for deps being built as subprojects:
   dependencies: TEPL_DEPS,
 )