Where is the right place to build C library in the snapcraft

I am trying to build this package into my snap, the instructions to build are:

git clone https://github.com/friendlyarm/WiringNP
cd WiringNP/
chmod 755 build

I have add this code inside parts: setup: override-build: | in plugin plugin: dump.

Inside the snap (--shell-after) I can use the library, but after installing the snap I get ProcessException: No such file or directory.

Where is the right place to include the library build process so that it will be accessible as C library and as command line interface (which is part of what the build does).

the wiringpi lib hacked up by friendlyarm seems to not respect the $DESTDIR variable in the Makefiles but instead hardcodes /usr… try removing the line below from all the Makefiles and the build should start putting the binary libs into the proper dirs fro shipping them inside a snap: