🐛 tilt: fix build_engine setting when using podman

[bengentil]

What this PR does / why we need it:

Following aa18c06 the podman detection has been moved below the default_build_engine variable usage,
breaking podman support.

This fix podman support by setting the build_engine directly instead of using a default_build_engine variable.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

[k8s-ci-robot]

Hi @bengentil. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[vincepri]

/ok-to-test

[sbueringer]

Ups, sorry for breaking this.

Thx for the fix!

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 85333073d6fd69aa43a0c8297b8d2771f6d4297a

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

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[johannesfrey]

/area devtools