Currently CMake scripts will generate both dynamic and static libraries
at the same time. However, CMake recommends using BUILD_SHARED_LIBS to
build either dynamic or static library, which is enforced by vcpkg.
Use BUILD_SHARED_LIBS to build one library type at a time, so that
developers can use vcpkg manifest mechanism to install Argtable3.
We also add namespace (argtable3::) to the package and generate CMake
config version file (Argtable3ConfigVersion.cmake), which can be used to determine the library version in find_package().
Tom G. Huang
1f73484b3b