package/ola: ftdidmx needs gcc >= 4.9

Fix the following build failure raised since re-introduction of the
package in commit 16ff948444c3978d63f483344a3d92d994c64312:

Makefile:575: *** libusb is in the dependency chain of libftdi1 that has added it to its _DEPENDENCIES variable without selecting it or depending on it from Config.in.  Stop.

Fixes:
 - http://autobuild.buildroot.org/results/f65baf4dd4c9a313745cdb9aefad2eae7a295469

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit ac98e808e4485cc93b5456f57d12cc247926c701)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/ola/Config.in

@@ -86,10 +86,14 @@ config BR2_PACKAGE_OLA_PLUGIN_ESPNET
 
 config BR2_PACKAGE_OLA_PLUGIN_FTDIDMX
 	bool "ftdidmx"
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9 # libftdi1 -> libusb
 	select BR2_PACKAGE_LIBFTDI1
 	help
 	  Build FTDI USB DMX plugin for OLA.
 
+comment "ftdidmx needs a toolchain w/ gcc >= 4.9"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_9
+
 config BR2_PACKAGE_OLA_PLUGIN_GPIO
 	bool "GPIO"
 	help