Revert "[microTVM] enable building microTVM components by default"

[areusch]

Reverts #13073 due to breakage of cases not covered by the CI. The cross-compile use case is particularly problematic.

Fixes #13482

@alanmacd @mehrdadh

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• cc @alanmacd, @gromero, @leandron, @mehrdadh _{See #10317 for details}
• Built docs for commit 3e3dd32 can be found here.
• This PR had no significant effect on CI runtime: -1.4% (167.35m -> 165.01m)

_{Generated by tvm-bot}

[areusch]

fixes #13482

[shingjan]

LGTM