synergy: needs gcc >= 4.9

Since version 1.9.0 and
https://github.com/symless/synergy-core/commit/c0376e9e2f659aec23a748f9a8d8ee6cd82f1281,
synergy needs C++14 so add a dependency on
BR2_TOOLCHAIN_GCC_AT_LEAST_4_9

Fixes:
 - http://autobuild.buildroot.org/results/c4646ee9342ea8bd906bfe2b29996c48cb403ccc

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Tested-by: Pieterjan Camerlynck <pieterjan.camerlynck@gmail.com>
Reviewed-by: Pieterjan Camerlynck <pieterjan.camerlynck@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/synergy/Config.in

@@ -4,6 +4,7 @@ config BR2_PACKAGE_SYNERGY
 	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_USE_WCHAR
 	depends on BR2_USE_MMU # fork()
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9 # C++14
 	select BR2_PACKAGE_XLIB_LIBX11
 	select BR2_PACKAGE_XLIB_LIBXTST
 	help
@@ -14,7 +15,8 @@ config BR2_PACKAGE_SYNERGY
 
 	  https://github.com/symless/synergy-core/
 
-comment "synergy needs a toolchain w/ C++, wchar"
+comment "synergy needs a toolchain w/ C++, wchar, gcc >= 4.9"
 	depends on BR2_PACKAGE_XORG7
 	depends on BR2_USE_MMU
-	depends on !(BR2_INSTALL_LIBSTDCPP && BR2_USE_WCHAR)
+	depends on !(BR2_INSTALL_LIBSTDCPP && BR2_USE_WCHAR && \
+		BR2_TOOLCHAIN_GCC_AT_LEAST_4_9)