Hacl ARM compilation issue

[orbifx 🦊 <fox@xxxxxxxxxxxxx>]

Hello!

I encountered a warning, which causes Hacl compilation failure on armv7l. I'm 
guessing it can't do a 64bit shift since it's 32bit?

Copying mirageos list as this appears to be a subproject.

```
[...]
kremlib.h:498:42: warning: right shift count >= width of type 
[-Wshift-count-overflow]
  498 |        ~(FStar_UInt64_eq_mask(x >> 64, y >> 64))) |
      |                                          ^~
kremlib.h:499:31: warning: right shift count >= width of type 
[-Wshift-count-overflow]
  499 |       (FStar_UInt64_eq_mask(x >> 64, y >> 64) & 
FStar_UInt64_gte_mask(x, y));
      |                               ^~
kremlib.h:499:40: warning: right shift count >= width of type 
[-Wshift-count-overflow]
  499 |       (FStar_UInt64_eq_mask(x >> 64, y >> 64) & 
FStar_UInt64_gte_mask(x, y));
      |                                        ^~
kremlib.h:500:28: warning: left shift count >= width of type 
[-Wshift-count-overflow]
  500 |   return ((uint128_t)mask) << 64 | mask;
      |                            ^~
```