There's a closed pull request on the void-packages repository

[RFC] add sse flags to i686 profile
https://github.com/void-linux/void-packages/pull/51333

Description:
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#### Testing the changes
- I tested the changes in this PR: **NO**

I don't actually have any i686 hardware to test with, but I've built a few packages without issues.

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There are several packages which require sse2 and fpmath flags to be added manually.

The void documentation quite clearly states that pentium 4 (sse2) is the base system requirements: https://docs.voidlinux.org/installation/index.html#base-system-requirements

If the base requirements are pentium4, we could alternately set gcc's `-march=pentium4` flag