gAR is a tool written in Go that uses ar to merge recursevily all object files produced in the specified directory in order to easily link the static library.
You can specify the directory (-d/--dir) where gAR should look for object files. You can specify the output pathname (-o/--out) of the file .a gAR will produce.
gar --dir ./libs/project/ -o ./libs/include/out.a