fix(build_package.sh): set CROSS_COMPILE directly to aarch64-none-elf-

The variable `aarch64_none_elf_prefix` was removed in recent changes,
causing CROSS_COMPILE to be unset during RMM builds. Update the script
to assign CROSS_COMPILE explicitly to "aarch64-none-elf-" to fix the
toolchain path and ensure build consistency.

Change-Id: I666395ccad09a3a860372cf5e0447d9cbf4a48fe
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/script/build_package.sh b/script/build_package.sh
index b3b1b1e..7087cc6 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -695,7 +695,7 @@
 	config_file="${rmm_build_config:-$rmm_config_file}"
 
 	# Build fiptool and all targets by default
-	export CROSS_COMPILE="${aarch64_none_elf_prefix}"
+	export CROSS_COMPILE="aarch64-none-elf-"
 
 	source "$config_file"