Encontrei. De acordo com o arquivo blt4l_1.3_Ubuntu-precise-steamrt
no link do site já existe um pré-construído libblt_loader.so
(2 semanas perdidas compilando este ) e um README.md
dizendo
Move the contents of this folder in to your PAYDAY 2 folder, so that it looks like this:
PAYDAY 2/ mods/ libblt_loader.so
Open Steam, and open the properties for PAYDAY 2. Select "Set Launch Options", and set it to:
env LD_PRELOAD="$LD_PRELOAD ./libblt_loader.so" %command%
If your PAYDAY 2 folder is in a different library folder, change the path accordingly.