Fix debug images

[jonjohnsonjr]

Fixes #810

[imjasonh]

Could add a test in cloudbuild.yaml that debug has a shell too to prevent future typos🤔

[codecov-io]

Codecov Report

Merging #811 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #811      +/-   ##
==========================================
+ Coverage   74.72%   74.77%   +0.04%     
==========================================
  Files         103      103              
  Lines        4313     4313              
==========================================
+ Hits         3223     3225       +2     
+ Misses        612      611       -1     
+ Partials      478      477       -1     

Impacted Files	Coverage Δ
pkg/v1/cache/fs.go	70.00% <0.00%> (+3.33%)	⬆️

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