make vendor_hwselect..., make menuconfig, make romfs, make,make, make linux image
The first "make romfs" is needed only to create the romfs dir, (mostly empty).
It is not needed afterward.
The first "make" may fail, if you have "Hyper-thread" or "Dual core" PC.
The next "make" will success.
But the initramfs may be empty, it was before real romfs generation.
The final "make linux image" will update the initramfs. You can use "make" as the final, but it is slower.
After the first successful boot image, you may change kernel or apps
make menuconfig,make,make linux image
You don't need make vendor_hwselect again, unless you change the ptf.
If you change ptf, then you need make clean, and start over from make vendor_hwselect.