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[bot]]

Codecov Report

:x: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 28.16%. Comparing base (974fa44) to head (48461ae). :warning: Report is 16 commits behind head on master.

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

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1246   +/-   ##
=======================================
  Coverage   28.16%   28.16%           
=======================================
  Files         267      267           
  Lines      202507   202507           
  Branches   202507   202507           
=======================================
  Hits        57028    57028           
  Misses      64141    64141           
  Partials    81338    81338           

Components	Coverage Δ
tectonic	50.89% <0.00%> (ø)
bridge_core	34.73% <ø> (ø)
bridge_flate	38.82% <ø> (ø)
bridge_fontconfig	83.06% <ø> (ø)
bridge_freetype2	92.00% <ø> (ø)
bridge_graphite2	∅ <ø> (∅)
bridge_harfbuzz	∅ <ø> (∅)
bridge_icu	∅ <ø> (∅)
bridge_png	100.00% <ø> (ø)
bundles	34.78% <ø> (ø)
cfg_support	94.84% <ø> (ø)
dep_support	0.00% <ø> (ø)
docmodel	84.09% <ø> (ø)
engine_bibtex	65.11% <ø> (ø)
engine_spx2html	0.00% <ø> (ø)
engine_xdvipdfmx	55.58% <ø> (ø)
engine_xetex	35.28% <ø> (ø)
errors	47.61% <ø> (ø)
geturl	27.16% <ø> (ø)
io_base	76.04% <ø> (ø)
pdf_io	14.31% <ø> (ø)
status_base	71.76% <ø> (ø)
xdv	0.00% <ø> (ø)
xetex_format	22.80% <ø> (ø)
xetex_layout	42.81% <ø> (ø)

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[CraftSpider]

Please rebase this on latest master, then I'll review it as soon as I'm able.

[lituzou]

now rebased