use gcc 4.9.3 for kinetis k70, newer gcc does not work with the old kernel from emcraft

target/config/Config.in.gcc

@@ -30,6 +30,7 @@ config ADK_TOOLCHAIN_GCC_5_3_0
 	depends on !ADK_TARGET_ARCH_H8300
 	depends on !ADK_TARGET_ARCH_METAG
 	depends on !ADK_TARGET_ARCH_OR1K
+	depends on !ADK_TARGET_SYSTEM_KINETIS_K70
 
 config ADK_TOOLCHAIN_GCC_4_9_3
 	bool "4.9.3"