CMake find_package doesn't work for a specific use-case

The find_package implementation doesn't work for @Alston-Tang, see comments from PR #33. CMake:

cmake_minimum_required(VERSION 3.16)

project(test)

find_package (pfs PATHS /home/alston64/works/pfs/build NO_DEFAULT_PATH REQUIRED)

include_directories ("/home/alston64/works/pfs/include")
add_executable(test test.cpp)
target_link_libraries(test "/home/alston64/works/pfs/build/lib/libpfs.a")