There is a new pull request by skmpz against master on the void-packages repository

https://github.com/skmpz/void-packages libpng-1.6.39
https://github.com/void-linux/void-packages/pull/40695

libpng: update to 1.6.39.
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#### Testing the changes
- I tested the changes in this PR: **YES**

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A patch file from https://github.com/void-linux/void-packages/pull/40695.patch is attached