minimal gcov gcda emitting emulation for wasm target

[nihui]

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.37%. Comparing base (2389090) to head (611aa58). Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #5903    +/-   ##
========================================
  Coverage   95.37%   95.37%            
========================================
  Files         818      818            
  Lines      268009   268365   +356     
========================================
+ Hits       255610   255966   +356     
  Misses      12399    12399            

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