LibCore: Use non-const char * for sethostname on Solaris

Author: https://github.com/ghost
Commit: https://github.com/SerenityOS/serenity/commit/8687dae0ca2
Pull-request: https://github.com/SerenityOS/serenity/pull/17623
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/elcuco
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibCore/System.cpp

@@ -576,7 +576,11 @@ ErrorOr<DeprecatedString> gethostname()
 
 ErrorOr<void> sethostname(StringView hostname)
 {
+#if defined(AK_OS_SOLARIS)
+    int rc = ::sethostname(const_cast<char*>(hostname.characters_without_null_termination()), hostname.length());
+#else
     int rc = ::sethostname(hostname.characters_without_null_termination(), hostname.length());
+#endif
     if (rc < 0)
         return Error::from_syscall("sethostname"sv, -errno);
     return {};