Custom NetBSD build hangs before booting

Hi,
I bought a Pinebook Pro and I wanted to build a custom image of NetBSD where binaries would be compiled with specific optimizations, but when I try to boot the laptop with the IMG image generated, the bootloader hangs with the following message:
*********************
Press return to boot now, any other key for boot prompt
booting netbsd - starting in 0 seconds. 
7687808+3423400+4187616+1768064 [598184+952584+711085]=0x13d6ed0
*********************

I cross-compiled this image from a NetBSD VM, with the generic official 10.0 image for ARM boards, virtualized with VMware Fusion Pro 13.6 on a MacBook Air M2.

Here some details:
* Git branch: netbsd-10

* Compiler: GCC

* Build cmdline: $HOME/source/src/build.sh -B $(PAGER="" git -C ./source/src log -1 | head -1 | awk '{ print $2 }' | cut -c1-12) -a aarch64 -m evbarm -O $HOME/build/obj -T $HOME/build/tools -D $HOME/build/dest -R $HOME/release -X $HOME/source/xsrc -U -V MAKECONF=$HOME/source/mk.conf -x -j3 release iso-image install-image

* mk.conf content:
CPUFLAGS=-march=armv8-a+simd+crypto
CPUFLAGS+=-mtune=cortex-a72.cortex-a53
CPUFLAGS+=-mcpu=cortex-a72.cortex-a53+crypto
#CPUFLAGS+=-mfpu=crypto-neon-fp-armv8 #disabled as not yet supported
MKDTRACE=yes

I also flashed the latest upstream version of Tow-Boot to the SPI as my main bootloader.

The values in $CPUFLAGS were set after reading:
1) https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf

2) https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html


Did someone else try to build a Pinebook Pro-specific build of NetBSD?
I'm new of the ARM world, so I messed up something for sure.
Any help is appreciated. :)


Best regards,
Luca De Pandis