Use strcspn(3) instead of non-portable strchrnul(3).

Index: src/terminal-util.cc
--- src/terminal-util.cc.orig
+++ src/terminal-util.cc
@@ -1181,7 +1181,7 @@ char *terminal_util_hyperlink_uri_label (const char *u
       g_ascii_strncasecmp(unesc, "https://", 8) == 0) {
     gs_free char *unidn = nullptr;
     char *hostname = strchr(unesc, '/') + 2;
-    char *hostname_end = strchrnul(hostname, '/');
+    char *hostname_end = hostname + strcspn(hostname, "/");
     char save = *hostname_end;
     *hostname_end = '\0';
     unidn = g_hostname_to_unicode(hostname);
@@ -1526,7 +1526,7 @@ terminal_util_find_program_in_path (const char *path,
       char *startp;
 
       path = p;
-      p = strchrnul (path, G_SEARCHPATH_SEPARATOR);
+      p = path + strcspn (path, G_SEARCHPATH_SEPARATOR_S);
 
       if (p == path)
         /* Two adjacent colons, or a colon at the beginning or the end