package/zeek: needs C++17

zeek needs C++17 since its addition in commit
ea36681572255ec906167308c07adc42ed2ac9f9 resulting in the following
build failure:

CMake Error at auxil/bifcl/cmake/RequireCXX17.cmake:46 (message):
  GCC version must be at least 7.0 for C++17 support, detected: 6.3.0

Fixes:
 - http://autobuild.buildroot.org/results/4d11e8bea1f7ed0b04cd7e123ed2f352e7a9e77f

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/zeek/Config.in

@@ -5,6 +5,8 @@ config BR2_PACKAGE_ZEEK
 	depends on !BR2_STATIC_LIBS
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_WCHAR
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_7 # C++17
+	depends on BR2_HOST_GCC_AT_LEAST_7 # host-zeek
 	select BR2_PACKAGE_LIBPCAP
 	select BR2_PACKAGE_MUSL_FTS if !BR2_TOOLCHAIN_USES_GLIBC
 	select BR2_PACKAGE_OPENSSL
@@ -33,7 +35,9 @@ config BR2_PACKAGE_ZEEK_ZEEKCTL
 
 endif
 
-comment "zeek needs a toolchain w/ C++, wchar, threads, dynamic library"
+comment "zeek needs a toolchain w/ C++, wchar, threads, dynamic library, gcc >= 7, host gcc >= 7"
 	depends on BR2_USE_MMU
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || \
-		!BR2_TOOLCHAIN_HAS_THREADS || BR2_STATIC_LIBS
+		!BR2_TOOLCHAIN_HAS_THREADS || BR2_STATIC_LIBS || \
+		!BR2_TOOLCHAIN_GCC_AT_LEAST_7 || \
+		!BR2_HOST_GCC_AT_LEAST_7