Resolves the following build error:
CMake Error at CMakeLists.txt:26 (ADD_EXECUTABLE):
Target "ARGPARSE_SAMPLE_custom_assignment_characters" links to target
"argparse::argparse" but the target was not found. Perhaps a
find_package() call is missing for an IMPORTED target, or an
ALIAS target is missing?
Signed-off-by: Sean Robinson <sean.robinson@scottsdalecc.edu>