The README even says: Install =======
The default installation will place headers in /usr/local/include and shared library in /usr/local/lib. It also installs a pkg-config script into /usr/local/lib/pkgconfig. Be aware that there are some larger tag families which may take a long time to build. If you do not want to use these tag families then you can speed up the installation by deleting the files tagCircle49h12.c, tagCircle49h12.h, tagCustom48h12.c, tagCustom48h12.h, tagStandard52h13.c, and tagStandard52h13.h before installing.