LibC: Add a stub for nice()

Author: https://github.com/danners
Commit: https://github.com/SerenityOS/serenity/commit/b9a8447dc0
Pull-request: https://github.com/SerenityOS/serenity/pull/14074

Userland/Libraries/LibC/unistd.cpp

@@ -995,4 +995,11 @@ int getdtablesize()
     int rc = getrlimit(RLIMIT_NOFILE, &dtablesize);
     __RETURN_WITH_ERRNO(rc, dtablesize.rlim_cur, rc);
 }
+
+// https://pubs.opengroup.org/onlinepubs/007904975/functions/nice.html
+int nice(int incr)
+{
+    dbgln("FIXME: nice was called with: {}, not implemented", incr);
+    return incr;
+}
 }

Userland/Libraries/LibC/unistd.h

@@ -120,6 +120,7 @@ char* getpass(char const* prompt);
 int pause(void);
 int chroot(char const*);
 int getdtablesize(void);
+int nice(int incr);
 
 enum {
     _PC_NAME_MAX,