fix(plugin-webpack): don't show the error message if packagerConfig.ignore is a function

[malept]

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Summarize your changes:

Fixes #2017

[codecov]

Codecov Report

Merging #2424 (253aff0) into master (182d437) will increase coverage by 2.31%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #2424      +/-   ##
==========================================
+ Coverage   72.76%   75.08%   +2.31%     
==========================================
  Files          91       91              
  Lines        2343     2348       +5     
  Branches      439      440       +1     
==========================================
+ Hits         1705     1763      +58     
- Misses        473      476       +3     
+ Partials      165      109      -56     

Impacted Files	Coverage Δ
packages/plugin/webpack/src/WebpackPlugin.ts	33.33% <50.00%> (-0.19%)	⬇️
packages/maker/base/src/Maker.ts	75.67% <0.00%> (-2.11%)	⬇️
packages/installer/darwin/src/InstallerDarwin.ts	31.57% <0.00%> (-1.76%)	⬇️
packages/api/core/src/util/upgrade-forge-config.ts	94.73% <0.00%> (-1.70%)	⬇️
packages/api/core/src/api/init.ts	97.56% <0.00%> (+4.87%)	⬆️
packages/api/core/src/api/make.ts	88.29% <0.00%> (+6.57%)	⬆️
packages/api/core/src/util/rebuild.ts	100.00% <0.00%> (+7.14%)	⬆️
packages/api/core/src/api/install.ts	94.87% <0.00%> (+16.66%)	⬆️
packages/api/core/src/api/start.ts	87.65% <0.00%> (+22.22%)	⬆️
packages/api/core/src/api/publish.ts	92.10% <0.00%> (+22.36%)	⬆️

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