There is an updated pull request by tibequadorian against master on the void-packages repository

https://github.com/tibequadorian/void-packages libgsm
https://github.com/void-linux/void-packages/pull/35647

libgsm: update to 1.0.19.
Old distfiles are apparently not deleted, so I changed them to upstream.
I also cleaned up the template a little bit and do the install using the Makefile target instead of doing this manually.
Currently libgsm-devel contains unnecessary header files, because all header files are just copied over.
Also includes manual pages now, which were not installed before.
I'm not sure what to put in license= ?

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A patch file from https://github.com/void-linux/void-packages/pull/35647.patch is attached