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

https://github.com/Chocimier/void-packages-org armadillo
https://github.com/void-linux/void-packages/pull/23820

armadillo: remove absolute paths form headers
It was #define ARMA_SUPERLU_INCLUDE_DIR /usr/arm-linux-gnueabihf/usr/include/
before. Absolute paths can't match usage of same package in both
cross and native environment at same time, let alone expansion of
'linux' macro. As all headers are installed into standard location,
relative path works.
Not suitable to upstream.

A patch file from https://github.com/void-linux/void-packages/pull/23820.patch is attached