multimedia/vmaf: unbreak build with clang 15 after a57fa880

../tools/cli_parse.c:194:21: error: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
    while ((key_val = strsep(&optarg_copy, ":")) != NULL) {
                    ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:195:15: error: incompatible integer to pointer conversion initializing 'char *' with an expression of type 'int' [-Wint-conversion]
        char *key = strsep(&key_val, "=");
              ^     ~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:196:15: error: incompatible integer to pointer conversion initializing 'char *' with an expression of type 'int' [-Wint-conversion]
        char *val = strsep(&key_val, "=");
              ^     ~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:221:19: error: incompatible integer to pointer conversion initializing 'char *' with an expression of type 'int' [-Wint-conversion]
            char *name = strsep(&key, ".");
                  ^      ~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:223:19: error: incompatible integer to pointer conversion initializing 'char *' with an expression of type 'int' [-Wint-conversion]
            char *opt = strsep(&key, ".");
                  ^     ~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:240:30: warning: call to undeclared function 'strnlen'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    const size_t optarg_sz = strnlen(optarg, 1024);
                             ^
../tools/cli_parse.c:249:17: warning: call to undeclared function 'strsep'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        .name = strsep(&optarg_copy, "="),
                ^
../tools/cli_parse.c:249:17: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Wint-conversion]
        .name = strsep(&optarg_copy, "="),
                ^~~~~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:255:21: error: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
    while ((key_val = strsep(&optarg_copy, ":")) != NULL) {
                    ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:256:21: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Wint-conversion]
        const char *key = strsep(&key_val, "=");
                    ^     ~~~~~~~~~~~~~~~~~~~~~
../tools/cli_parse.c:257:21: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Wint-conversion]
        const char *val = strsep(&key_val, "=");
                    ^     ~~~~~~~~~~~~~~~~~~~~~

Reported by:	Michael Butler