fix: monorepo use different cwd

[czy88840616]

修复在不同的 monorepo cwd 场景下，启动 eggjs 的问题。

related: eggjs/egg#4274

[gitpod-io]

[codecov-io]

Codecov Report

Merging #752 (f7288ee) into 2.x (af7a462) will increase coverage by 0.48%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              2.x     #752      +/-   ##
==========================================
+ Coverage   85.99%   86.47%   +0.48%     
==========================================
  Files         144      144              
  Lines        5906     5902       -4     
  Branches     1094     1092       -2     
==========================================
+ Hits         5079     5104      +25     
+ Misses        792      766      -26     
+ Partials       35       32       -3     

Impacted Files	Coverage Δ
packages/web/src/base.ts	89.13% <100.00%> (-0.31%)	⬇️
packages/web/config/config.default.js	100.00% <0.00%> (+6.25%)	⬆️
packages/web/app.js	78.12% <0.00%> (+9.37%)	⬆️
packages/web/src/devFramework.ts	66.66% <0.00%> (+22.22%)	⬆️
packages/web/src/framework.ts	87.83% <0.00%> (+25.67%)	⬆️

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[waitingsong]

v2.5.4 版本下 monorep+egg 正常了。