package/libzenoh-pico: add threads comment

Commit 3e76df02b324b0442eec7bfd2451ee2fbb3709e9 forgot to add a comment
about threads dependency

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libzenoh-pico/Config.in

@@ -9,3 +9,6 @@ config BR2_PACKAGE_LIBZENOH_PICO
 	  functionalities.
 
 	  https://github.com/eclipse-zenoh/zenoh-pico
+
+comment "libzenoh-pico needs a toolchain w/ threads"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS