Okay, I got everything work so far building a room with aarch64-4.9 for both rom and kernel. But when I try to switch to 5.3 for kernel, I run in some issues. If I enable ARCHIDROID_GCC_CFLAGS_32 I get the error that this are unsupported options while compiling the rom. If I disable them, the kernel build fails with a parenthesis error. Am I thinking right that moving the flags from ARCHIDROID_GCC_CFLAGS_32 to ARCHIDROID_GCC_CFLAGS_64 might do the trick?