package/collectd: add missing comment for mysql dependencies

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/collectd/Config.in

@@ -384,6 +384,10 @@ config BR2_PACKAGE_COLLECTD_MYSQL
 	  Connects to a MySQL database and issues a "show status"
 	  command.
 
+comment "mysql needs a toolchain w/ C++, threads"
+	depends on BR2_USE_MMU
+	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS
+
 config BR2_PACKAGE_COLLECTD_NETLINK
 	bool "netlink"
 	select BR2_PACKAGE_LIBMNL