toolchain: add gcc 9 entry

In order to add gcc 9 support for internal and external toolchain in
follow-up commits, introduce BR2_TOOLCHAIN_GCC_AT_LEAST_9 symbol.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

toolchain/Config.in

@@ -521,10 +521,15 @@ config BR2_TOOLCHAIN_GCC_AT_LEAST_8
 	bool
 	select BR2_TOOLCHAIN_GCC_AT_LEAST_7
 
+config BR2_TOOLCHAIN_GCC_AT_LEAST_9
+	bool
+	select BR2_TOOLCHAIN_GCC_AT_LEAST_8
+
 # 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 "9"	if BR2_TOOLCHAIN_GCC_AT_LEAST_9
 	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