sed on Makefile looks wrong

[hatoo]

Hi, thanks for publishing this repository!
During testing on my side, it seems that the Makefile is wrong.

I'm not very familiar with sed, but I think

tiny-gpu/Makefile

Line 14 in de7cf22

sed -i '' '1s/^/`timescale 1ns\/1ns\n/' build/gpu.v

should be

sed -i '1s/^/`timescale 1ns\/1ns\n/' build/gpu.v

and I've also noticed that running a simulation requires compiling https://github.com/zachjs/sv2v from the source
because it seems using https://github.com/zachjs/sv2v/blob/261beffd0f4dd26bd1a19d574bbcc2caabba2eaa/CHANGELOG.md?plain=1#L42 which is not released yet. I think this information is good to add somewhere in README.

[xianbaoqian]

I managed to run this on my macbook. Created a PR with some instructions: #2