package/ola: usbpro needs gcc >= 4.9

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

configure: error: compiler with C11 support is required to build libusb

Fixes:
 - http://autobuild.buildroot.org/results/e9239403bb13d3468db01a952da8c695c0e5ea30

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/ola/Config.in

@@ -164,8 +164,12 @@ config BR2_PACKAGE_OLA_PLUGIN_USBDMX
 
 config BR2_PACKAGE_OLA_PLUGIN_USBPRO
 	bool "usbpro"
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9 # libusb
 	select BR2_PACKAGE_LIBUSB
 	help
 	  Build UsbPro plugin for OLA.
 
+comment "usbpro needs a toolchain w/ gcc >= 4.9"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_9
+
 endif