fix: 修复无法通过设置环境变量构建单个包

[wangxingkang]

No description provided.

[wangxingkang]

修复 #344

[codecov]

Codecov Report

Merging #351 (60904f2) into master (245a681) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #351   +/-   ##
=======================================
  Coverage   74.01%   74.01%           
=======================================
  Files          16       16           
  Lines         481      481           
  Branches      171      171           
=======================================
  Hits          356      356           
  Misses        124      124           
  Partials        1        1           

Impacted Files	Coverage Δ
packages/father-build/src/build.ts	97.67% <100.00%> (ø)

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