cmake: Add arm64 cross-compile target

There is an ongoing effort in Zephyr to separate the ARM architecture
from ARM64 (AArch64). As part of this work, a new architecture will be
introduced called 'arm64'. To be able to keep using the same SDK to
compile old and new Zephyr releases, we need to add a new cross-compile
target specifically for 'arm64' together with the legacy 'arm' target.

Signed-off-by: Carlo Caione <[email protected]>

Author: carlocaione

cmake/zephyr/target.cmake

@@ -1,10 +1,12 @@
 # SPDX-License-Identifier: Apache-2.0
 
 if(CONFIG_ARM64)
+  # Legacy target to support Zephyr versions before the ARM/ARM64 split
   set(CROSS_COMPILE_TARGET_arm         aarch64-zephyr-elf)
 else()
   set(CROSS_COMPILE_TARGET_arm         arm-zephyr-eabi)
 endif()
+set(CROSS_COMPILE_TARGET_arm64   aarch64-zephyr-elf)
 set(CROSS_COMPILE_TARGET_nios2     nios2-zephyr-elf)
 set(CROSS_COMPILE_TARGET_riscv   riscv64-zephyr-elf)
 set(CROSS_COMPILE_TARGET_mips       mips-zephyr-elf)