std::alloc: checking if the alignment is, at least, a word size.

so we do not error (at least on solarish systems) in that case.
close rust-langGH-124787

library/std/src/sys/pal/unix/alloc.rs

@@ -1,4 +1,5 @@
 use crate::alloc::{GlobalAlloc, Layout, System};
+use crate::mem;
 use crate::ptr;
 use crate::sys::common::alloc::{realloc_fallback, MIN_ALIGN};
 
@@ -81,7 +82,7 @@ cfg_if::cfg_if! {
             // [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579
             // [4]: https://chromium.googlesource.com/chromium/src/base/+/master/
             //                                       /memory/aligned_memory.cc
-            libc::memalign(layout.align(), layout.size()) as *mut u8
+            if layout.align() >= mem::size_of::<usize>() { libc::memalign(layout.align(), layout.size()) as *mut u8 } else { ptr::null_mut() }
         }
     } else if #[cfg(target_os = "wasi")] {
         #[inline]