Build issues on Linux

[JT8D-17]

I'm trying to build the plugin (commit: 4f44d95 ) on Arch Linux. The gtest package is installed.

What I did:

Git clone https://github.com/felix-b/atc.git
cd ./atc
git submodule init
git submodule update
cmake .

Output:

CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
PPL_LIBRARY
linked by target "pluginxp" in directory /media/Data/Git_Repos/atc/src/pluginxp
SPEECH_LIBRARY
linked by target "pluginxp" in directory /media/Data/Git_Repos/atc/src/pluginxp

I see these variables mentioned in src/pluginxp/CMakeLists.txt, but I have no idea where from and how they're inherited.