package/gcc: add logic to hide gcc 15 for unsupported CPUs

This logic is to prepare for future gcc versions and their new
supported CPUs. As of today, gcc 15 is the latest gcc version
and all architectures and CPUs in Buildroot are supported by
this version.

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

package/gcc/Config.in.host

@@ -43,6 +43,7 @@ config BR2_GCC_VERSION_14_X
 
 config BR2_GCC_VERSION_15_X
 	bool "gcc 15.x"
+	depends on !BR2_ARCH_NEEDS_GCC_AT_LEAST_16
 	# powerpc spe support has been deprecated since gcc 8.x.
 	# https://gcc.gnu.org/ml/gcc/2018-04/msg00102.html
 	depends on !BR2_POWERPC_CPU_HAS_SPE