all: make vendored copy of reexec

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #1782 (524f459) into master (7755bcc) will increase coverage by 0.01%.
Report is 351 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1782      +/-   ##
==========================================
+ Coverage   52.69%   52.70%   +0.01%     
==========================================
  Files         485      485              
  Lines       60514    60514              
==========================================
+ Hits        31887    31894       +7     
- Misses      26165    26167       +2     
+ Partials     2462     2453       -9     

Files	Coverage Δ
p2p/simulations/adapters/exec.go	0.73% <ø> (ø)
p2p/simulations/adapters/types.go	0.00% <ø> (ø)

... and 13 files with indirect coverage changes