cutelyst: depends on C++11

thread-local storage is a C++11 feature available since gcc 4.8:
https://gcc.gnu.org/projects/cxx-status.html#cxx11

Fixes:
 - http://autobuild.buildroot.net/results/2963bd55cd7c33ded3e5a75fc86079acfae844c1

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

package/cutelyst/Config.in

@@ -1,6 +1,8 @@
 config BR2_PACKAGE_CUTELYST
 	bool "cutelyst"
 	depends on BR2_PACKAGE_QT5
+	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 # C++11
 	select BR2_PACKAGE_OPENSSL
 	select BR2_PACKAGE_QT5BASE_GUI
 	help
@@ -8,3 +10,7 @@ config BR2_PACKAGE_CUTELYST
 	  the simple approach of Catalyst (Perl) framework.
 
 	  https://cutelyst.org
+
+comment "cutelyst needs a toolchain w/ C++, gcc >= 4.8"
+	depends on BR2_PACKAGE_QT5
+	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8