do not put any stdlibs in the base sysimage

[KristofferC]

Also, when putting default stdlibs in the sysimage, only use the ones from the default sysimage

Fixes #1062

[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.21%. Comparing base (4161ffd) to head (dbea5f0).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/PackageCompiler.jl	88.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1063      +/-   ##
==========================================
- Coverage   86.21%   86.21%   -0.01%     
==========================================
  Files           3        3              
  Lines         798      805       +7     
==========================================
+ Hits          688      694       +6     
- Misses        110      111       +1     

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