x11-toolkits/wlroots018: unbreak build with clang 21

../xcursor/xcursor.c:605:8: error: initializing 'char *' with an expression of type 'const char *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]

605 |         char *colon = strchr(path, ':');
    |               ^       ~~~~~~~~~~~~~~~~~

Reported by: pkg-fallout