libelf and zlib are internal dependencies of libbpf and thus are required to link against and must be installed on the system for applications to work. pkg-config is used by default to find libelf, and the program called can be overridden with PKG_CONFIG.
If using pkg-config at build time is not desired, it can be disabled by setting NO_PKG_CONFIG=1 when calling make.
To build both static libbpf.a and shared libbpf.so:
$ cd src $ make
To build only static libbpf.a library in directory build/ and install them together with libbpf headers in a staging directory root/:
$ cd src $ mkdir build root $ BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=root make install
To build both static libbpf.a and shared libbpf.so against a custom libelf dependency installed in /build/root/ and install them together with libbpf headers in a build directory /build/root/:
$ cd src $ PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make