linux-dev package has extra files in it
See https://pkgs.alpinelinux.org/contents?branch=edge&name=linux-vanilla-dev&arch=x86&repo=main the Linux dev file is full of Makefile and Kconfig files which should be excluded by the find expression here http://git.alpinelinux.org/cgit/aports/tree/main/linux-vanilla/APKBUILD?id=5e16e2a862a9efa6df6363a57ab7b7ae22fdb739\#n146 but it is not correctly constructed. It is modelled after the Ubuntu/Debian ones which just contain the header files eg https://packages.debian.org/jessie/amd64/linux-headers-3.16.0-4-amd64/filelist
(from redmine: issue id 6614, created on 2017-01-03)