Bug: resolve issue aarch64-darwin hash mismatch

@winterqt discovered that all the FOD branding assets failed to build on aarch64-darwin due to hash mismatches. After comparing their output with my own builds on x86_64-linux, we found that it was due to floating point differences.

The easiest fix might be to add a simple function that can round to significant figures. This implementation should work.

def round_to_sigfig(x, s):
    return round(x, s - 1 - int(floor(log10(abs(x)))))

After some basic testing, it appears to work. Also not shown is it working for negative numbers.

>>> def round_to_sigfig(x, s):
...   return round(x, s - 1 -int(floor(log10(abs(x)))))
... 
>>> round_to_sigfig(1111.1111, 8)
1111.1111
>>> round_to_sigfig(1111.1111, 7)
1111.111
>>> round_to_sigfig(1111.1111, 4)
1111.0
>>> round_to_sigfig(1111.1111, 2)
1100.0

Double precision in IEEE 754 should give between 15-17 digits of precision. Using 12 significant figures should be sufficient. It will solve the rounding differences, give us a few digits of padding in case anything weird happens, but still have enough precision that we will never have to worry about a lack of co-linear lines.

No source file or test is named; start by tracing the FOD branding asset build and reproducing the hash mismatch on aarch64-darwin versus x86_64-linux. Evaluate the proposed significant-figure rounding approach, including negative values, and consider the issue done when the generated assets have matching hashes across both platforms.