wdmd: include libgen.h for basename
    
    basename prototype has been removed from string.h from latest musl [1]
    compilers e.g. clang-18 flags the absense of prototype as error. therefore
    include libgen.h for providing it.
    
    [1] https://git.musl-libc.org/cgit/musl/commit/?id=725e17ed6dff4d0cd22487bb64470881e86a92e7
    
    Signed-off-by: Khem Raj <raj.khem@gmail.com>