Try to fix u-boot cross-build

Author: lool

scripts/build-u-boot-rb1.sh

@@ -70,7 +70,8 @@ log_i "Configuring U-Boot (${CONFIG})"
 make "${CONFIG}"
 
 log_i "Building U-Boot (with device tree ${U_BOOT_DEVICE_TREE})"
-make -j`nproc` DEVICE_TREE="${U_BOOT_DEVICE_TREE}"
+make -j`nproc` \
+    CROSS_COMPILE=aarch64-linux-gnu- DEVICE_TREE="${U_BOOT_DEVICE_TREE}"
 
 log_i "Creating Android boot image (${ABOOT_OUTPUT})"
 gzip u-boot-nodtb.bin