toolchain/toolchain-external/toolchain-external-custom: add gcc 14 version selection
This patch allows to use an external toolchain based on gcc 14.
Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>
Tested-by: Vincent Stehlé <vincent.stehle@arm.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>