[Android Software/Hacking General [Developers Only]] RogerF81:
First of all, thank you so much for your answer! :)

To point 1: Didn't I do that? Or am I missing something?

To point 2: I missed at least this :D Thanks for the heads-up. So either I use the same tc which Sultan used, or I have revert these specific commits, to be able to use Clang.

EDIT: Ok, now I tried to compile with GCC. This is what I did (of course in the correct toolchain folders):

export CROSS_COMPILE=$(pwd)/bin/aarch64-linux-
export CROSS_COMPILE_ARM32=$(pwd)/bin/arm-linux-gnueabi-

and then in the kernel folder:

export ARCH=arm64 && export SUBARCH=arm64
make clean

with the following output:

ake[1]: Entering directory '/home/rogerf81/sultan/sultan_kernel/out'
CLEAN .
CLEAN arch/arm64/kernel/vdso
CLEAN arch/arm64/kernel/vdso32
find: ‘arch/arm64/boot/dts/’: No such file or directory
find: ‘arch/arm64/boot/dts/’: No such file or directory
CLEAN .tmp_versions
make[1]: Leaving directory '/home/rogerf81/sultan/sultan_kernel/out

'

make mrproper

with following output:

make[1]: Entering directory '/home/rogerf81/sultan/sultan_kernel/out'
find: ‘arch/arm64/boot/dts/’: No such file or directory
find: ‘arch/arm64/boot/dts/’: No such file or directory
CLEAN scripts/basic
CLEAN scripts/kconfig
CLEAN include/config include/generated arch/arm64/include/generated
CLEAN .config
make[1]: Leaving directory '/home/rogerf81/sultan/sultan_kernel/out'

make wahoo_defconfig

output:

make[1]: Entering directory '/home/rogerf81/sultan/sultan_kernel/out'
HOSTCC scripts/basic/fixdep
GEN ./Makefile
HOSTCC scripts/kconfig/conf.o
SHIPPED scripts/kconfig/zconf.tab.c
SHIPPED scripts/kconfig/zconf.lex.c
SHIPPED scripts/kconfig/zconf.hash.c
HOSTCC scripts/kconfig/zconf.tab.o
HOSTLD scripts/kconfig/conf
#
# configuration written to .config
#
make[1]: Leaving directory '/home/rogerf81/sultan/sultan_kernel/out'

And finally,

make -j$(nproc --all)

with the final output + errors:

make[1]: Entering directory '/home/rogerf81/sultan/sultan_kernel/out'
GEN ./Makefile
scripts/kconfig/conf --silentoldconfig Kconfig
CHK include/config/kernel.release
UPD include/config/kernel.release
Using .. as source for kernel
GEN ./Makefile
WRAP arch/arm64/include/generated/asm/bug.h
WRAP arch/arm64/include/generated/asm/bugs.h
WRAP arch/arm64/include/generated/asm/clkdev.h
WRAP arch/arm64/include/generated/asm/cputime.h
WRAP arch/arm64/include/generated/asm/current.h
WRAP arch/arm64/include/generated/asm/delay.h
WRAP arch/arm64/include/generated/asm/div64.h
WRAP arch/arm64/include/generated/asm/dma.h
WRAP arch/arm64/include/generated/asm/dma-contiguous.h
WRAP arch/arm64/include/generated/asm/early_ioremap.h
WRAP arch/arm64/include/generated/asm/emergency-restart.h
WRAP arch/arm64/include/generated/asm/errno.h
WRAP arch/arm64/include/generated/asm/ftrace.h
WRAP arch/arm64/include/generated/asm/hash.h
WRAP arch/arm64/include/generated/asm/hw_irq.h
WRAP arch/arm64/include/generated/asm/ioctl.h
WRAP arch/arm64/include/generated/asm/ioctls.h
WRAP arch/arm64/include/generated/asm/ipcbuf.h
WRAP arch/arm64/include/generated/asm/irq_regs.h
WRAP arch/arm64/include/generated/asm/kdebug.h
WRAP arch/arm64/include/generated/asm/kmap_types.h
WRAP arch/arm64/include/generated/asm/kvm_para.h
WRAP arch/arm64/include/generated/asm/local.h
WRAP arch/arm64/include/generated/asm/local64.h
WRAP arch/arm64/include/generated/asm/mcs_spinlock.h
WRAP arch/arm64/include/generated/asm/mm-arch-hooks.h
WRAP arch/arm64/include/generated/asm/mman.h
WRAP arch/arm64/include/generated/asm/msgbuf.h
WRAP arch/arm64/include/generated/asm/msi.h
WRAP arch/arm64/include/generated/asm/mutex.h
WRAP arch/arm64/include/generated/asm/pci.h
WRAP arch/arm64/include/generated/asm/pci-bridge.h
WRAP arch/arm64/include/generated/asm/poll.h
WRAP arch/arm64/include/generated/asm/preempt.h
WRAP arch/arm64/include/generated/asm/resource.h
WRAP arch/arm64/include/generated/asm/rwsem.h
WRAP arch/arm64/include/generated/asm/sections.h
WRAP arch/arm64/include/generated/asm/segment.h
WRAP arch/arm64/include/generated/asm/sembuf.h
WRAP arch/arm64/include/generated/asm/serial.h
WRAP arch/arm64/include/generated/asm/shmbuf.h
WRAP arch/arm64/include/generated/asm/simd.h
WRAP arch/arm64/include/generated/asm/sizes.h
WRAP arch/arm64/include/generated/asm/socket.h
WRAP arch/arm64/include/generated/asm/sockios.h
WRAP arch/arm64/include/generated/asm/swab.h
WRAP arch/arm64/include/generated/asm/switch_to.h
WRAP arch/arm64/include/generated/asm/termbits.h
WRAP arch/arm64/include/generated/asm/termios.h
WRAP arch/arm64/include/generated/asm/topology.h
WRAP arch/arm64/include/generated/asm/trace_clock.h
WRAP arch/arm64/include/generated/asm/types.h
WRAP arch/arm64/include/generated/asm/unaligned.h
WRAP arch/arm64/include/generated/asm/user.h
WRAP arch/arm64/include/generated/asm/vga.h
WRAP arch/arm64/include/generated/asm/xor.h
WRAP arch/arm64/include/generated/uapi/asm/kvm_para.h
CHK include/generated/uapi/linux/version.h
UPD include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
UPD include/generated/utsrelease.h
HOSTCC scripts/basic/bin2c
CC kernel/bounds.s
CHK include/generated/bounds.h
UPD include/generated/bounds.h
CHK include/generated/timeconst.h
UPD include/generated/timeconst.h
CC arch/arm64/kernel/asm-offsets.s
CHK include/generated/asm-offsets.h
UPD include/generated/asm-offsets.h
CALL ../scripts/checksyscalls.sh
LDS arch/arm64/kernel/vdso/vdso.lds
VDSOC arch/arm64/kernel/vdso/vgettimeofday.o
VDSOA arch/arm64/kernel/vdso/note.o
VDSOA arch/arm64/kernel/vdso/sigreturn.o
VDSOL arch/arm64/kernel/vdso/vdso.so.dbg
VDSOSYM include/generated/vdso-offsets.h
LDS arch/arm64/kernel/vdso32/vdso.lds
VDSOC32 arch/arm64/kernel/vdso32/vgettimeofday.o
VDSOA32 arch/arm64/kernel/vdso32/sigreturn.o
VDSOL32 arch/arm64/kernel/vdso32/vdso.so.raw
HOSTCC arch/arm64/kernel/vdso32/../../../arm/vdso/vdsomunge
MUNGE arch/arm64/kernel/vdso32/vdso.so.dbg
VDSOSYM include/generated/vdso32-offsets.h
make[3]: *** No rule to make target 'scripts/dtc-aosp/dtc/dtc.c', needed by 'scripts/dtc-aosp/dtc/dtc.o'. Stop.
make[2]: *** [../scripts/Makefile.build:559: scripts/dtc-aosp] Error 2
make[1]: *** [/home/rogerf81/sultan/sultan_kernel/Makefile:565: scripts] Error 2
make[1]: Leaving directory '/home/rogerf81/sultan/sultan_kernel/out'
make: *** [Makefile:154: sub-make] Error 2

What did I do wrong this time? Do I use the wrong toolchain perhaps? I'm using the tc linked by Sultan for cross_compile and the gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabi tc for cross_compile_arm32.

Or did I point something wrong? Thanks in advance for any help :)