arch: add BR2_ARCH_NEEDS_GCC_AT_LEAST_9

This new symbol will be used by architectures introduced with gcc 9 and
by external toolchains based on gcc 9.

[1] https://gcc.gnu.org/gcc-9/changes.html

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>

arch/Config.in

@@ -301,6 +301,10 @@ config BR2_ARCH_NEEDS_GCC_AT_LEAST_8
 	bool
 	select BR2_ARCH_NEEDS_GCC_AT_LEAST_7
 
+config BR2_ARCH_NEEDS_GCC_AT_LEAST_9
+	bool
+	select BR2_ARCH_NEEDS_GCC_AT_LEAST_8
+
 # The following string values are defined by the individual
 # Config.in.$ARCH files
 config BR2_ARCH

package/gcc/Config.in.host

@@ -75,6 +75,7 @@ config BR2_GCC_VERSION_7_X
 
 config BR2_GCC_VERSION_8_X
 	bool "gcc 8.x"
+	depends on !BR2_ARCH_NEEDS_GCC_AT_LEAST_9
 	# Broken or unsupported architectures
 	depends on !BR2_csky
 	depends on !BR2_or1k