Build-time __dirname in browser test builds

[rtsao]

Tape needs __dirname to function properly

Fixes #66

[codecov]

Codecov Report

Merging #65 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
+ Coverage   68.91%   68.94%   +0.02%     
==========================================
  Files          64       64              
  Lines        1377     1378       +1     
  Branches      299      300       +1     
==========================================
+ Hits          949      950       +1     
  Misses        374      374              
  Partials       54       54

Impacted Files	Coverage Δ
build/compiler.js	88.51% <100%> (+0.04%)	⬆️

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[rtsao]

!merge