Fix Konflux build platform arch (main branch)

[simonbaird]

The GOOS and GOARCH env vars need to be set explicitly, otherwise we just build the linux x86 binary over and over. Looks like this regression was introduced in commit b8db99c.

I think restoring the export on those two vars would also have worked.

Ref: https://issues.redhat.com/browse/SECURESIGN-1054

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.66%. Comparing base (3f31ea4) to head (d62ea87).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1696      +/-   ##
==========================================
+ Coverage   80.01%   86.66%   +6.64%     
==========================================
  Files          65       76      +11     
  Lines        4818     5158     +340     
==========================================
+ Hits         3855     4470     +615     
+ Misses        963      688     -275     

Flag	Coverage Δ
acceptance	71.77% <ø> (?)
generative	80.01% <ø> (ø)
integration	80.01% <ø> (ø)
unit	80.01% <ø> (ø)

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see 41 files with indirect coverage changes