toolchain/Config.in: add BR2_TOOLCHAIN_GCC_AT_LEAST_10 blind option

In order to add gcc 10 support for internal and external toolchain in
follow-up commits, introduce BR2_TOOLCHAIN_GCC_AT_LEAST_10 symbol.

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

toolchain/Config.in

@@ -591,10 +591,15 @@ config BR2_TOOLCHAIN_GCC_AT_LEAST_9
 	bool
 	select BR2_TOOLCHAIN_GCC_AT_LEAST_8
 
+config BR2_TOOLCHAIN_GCC_AT_LEAST_10
+	bool
+	select BR2_TOOLCHAIN_GCC_AT_LEAST_9
+
 # 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 "10"	if BR2_TOOLCHAIN_GCC_AT_LEAST_10
 	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