fix: Exclude example flags provided by node

[sttk]

This PR is to fix the issue #65.

In recent Node.js, the output of node --v8-options contains extra lines in the --xxx format, like:

% node --v8-options
SSE3=1 SSSE3=1 SSE4_1=1 SSE4_2=1 SAHF=1 AVX=1 AVX2=1 FMA3=1 BMI1=1 BMI2=1 LZCNT=1 POPCNT=1 ATOM=0
The following syntax for options is accepted (both '-' and '--' are ok):
  --flag        (bool flags only)
  --no-flag     (bool flags only)
  --flag=value  (non-bool flags only, no spaces around '=')
  --flag value  (non-bool flags only)
  --            (captures all remaining args in JavaScript)

Options:
  --abort-on-contradictory-flags (Disallow flags or implications overriding each other.)
        type: bool  default: --noabort-on-contradictory-flags
  ...

Regarding this issue, we had implemented a solution to extract options from Options: onward, but there was a mistake in that. This PR is to correct that mistake.

Closes #65

[phated]

This needs a test. I'll look into adding it.