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

common/build-style/gnu-makefile.sh: define prefix, PREFIX for build
https://github.com/void-linux/void-packages/pull/38823

Description:
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#### Testing the changes
- I tested the changes in this PR: **briefly**

Should fix some issues where PREFIX or prefix is used during build, like with netsurf (b7853685fb20db4c91bbc5a1cd7a9cfe6c15cbd1)

[ci skip]