LibC: Stub out posix_memalign()

Userland/Libraries/LibC/stdlib.cpp

@@ -1335,3 +1335,12 @@ void _Exit(int status)
 {
     _exit(status);
 }
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_memalign.html
+int posix_memalign(void** memptr, size_t alignment, size_t size)
+{
+    (void)memptr;
+    (void)alignment;
+    (void)size;
+    TODO();
+}

Userland/Libraries/LibC/stdlib.h

@@ -101,4 +101,6 @@ int posix_openpt(int flags);
 int grantpt(int fd);
 int unlockpt(int fd);
 
+int posix_memalign(void**, size_t alignment, size_t size);
+
 __END_DECLS