Fix #809

[st0012]

This PR fixes #809 and several other issues:

1. goby_test.go's init setup didn't rebuild a clean binary before each run, so I fixed it.
2. TestArgI test case wasn't working, fixed it as well.

[codecov]

Codecov Report

Merging #811 into master will increase coverage by 0.02%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #811      +/-   ##
==========================================
+ Coverage   80.89%   80.92%   +0.02%     
==========================================
  Files          54       54              
  Lines        7403     7402       -1     
==========================================
+ Hits         5989     5990       +1     
+ Misses       1189     1188       -1     
+ Partials      225      224       -1

Impacted Files	Coverage Δ
vm/thread.go	87.22% <ø> (+1.13%)	⬆️
vm/vm.go	82.53% <33.33%> (-0.35%)	⬇️

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[hachi8833]

LGTM. Thank you for the quick fix!