Can't build 0.25 on Alpine Linux

[jeffrizzo]

When trying to build 0.25 under Docker using Alpine Linux (it built in version 0.23), I got this error, so I'm reporting it as requested:

#11 8.002 -- Looking for pthread_setname_np
#11 8.206 -- Looking for pthread_setname_np - found
#11 8.212 -- found unknown distribution Alpine Linux, Version : VERSION_ID=3.20.0
#11 8.212 CMake Error at cmake/LinuxPackaging.cmake:35 (message):
#11 8.212   please report an error to
#11 8.212   https:\/\/github.com\/analogdevicesinc\/libiio\/issues
#11 8.212 Call Stack (most recent call first):
#11 8.212   CMakeLists.txt:650 (include)