toolchain: add gcc 8 entry

In order to add gcc 8 support for internal and external toolchain in
follow-up commits, introduce BR2_TOOLCHAIN_GCC_AT_LEAST_8 symbol.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

toolchain/Config.in

@@ -404,10 +404,15 @@ config BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	bool
 	select BR2_TOOLCHAIN_GCC_AT_LEAST_6
 
+config BR2_TOOLCHAIN_GCC_AT_LEAST_8
+	bool
+	select BR2_TOOLCHAIN_GCC_AT_LEAST_7
+
 # This order guarantees that the highest version is set, as kconfig
 # stops affecting a value on the first matching default.
 config BR2_TOOLCHAIN_GCC_AT_LEAST
 	string
+	default "8"	if BR2_TOOLCHAIN_GCC_AT_LEAST_8
 	default "7"	if BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	default "6"	if BR2_TOOLCHAIN_GCC_AT_LEAST_6
 	default "5"	if BR2_TOOLCHAIN_GCC_AT_LEAST_5