[llvm] [BOLT][NFC] Set minimal alignment for BF (PR #67707)

[via llvm-commits]

maksfb wrote:

Do you anticipate different CIs to have different min alignments in the future? If not, I would rather modify the newly added `getMinAlignment()` to return a correct value based on the underlying arch and the type of object. Turning `MinAlign` into a field needs a justification.

https://github.com/llvm/llvm-project/pull/67707