V2 bundle create: fix build_dir in select and pack actions

[lituzou]

tectonic is unable to find the build directory correctly due to the use of cli.build_dir instead of the local build_dir joined with bundle name.

This PR addresses this bug.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 46.14%. Comparing base (ddca0b8) to head (c70239b).

Files with missing lines	Patch %	Lines
src/bin/tectonic/v2cli/commands/bundle/actions.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1246      +/-   ##
==========================================
- Coverage   46.20%   46.14%   -0.06%     
==========================================
  Files         186      186              
  Lines       66139    66138       -1     
==========================================
- Hits        30561    30521      -40     
- Misses      35578    35617      +39     

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