Either clone this repository recursively:
git clone --recursive https://github.com/ampl/plugins.git
or, after cloning, check out the submodules:
git submodule update --init
To generate build files using cmake, for Linux/Unix/OSX systems (change 64 to 32 if a 32 bits build is needed):
mkdir build
cd build
cmake .. -DARCH=64
On Windows, with Visual Studio 2017+:
mkdir build
cd build
cmake ..
add -A Win32 to the cmake statement to generate 32 bits libraries.