Try to avoid undefined behavior in runtime intrinsics (#31548)
The analyzer complains
```
/home/keno/julia/src/runtime_intrinsics.c:886:38: note: The result of the left shift is undefined because the left operand is
negative
checked_iintrinsic_fast(LLVMSub_sov, check_ssub_int, sub, checked_ssub_int, )
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/keno/julia/src/runtime_intrinsics.c:510:25: note: expanded from macro 'checked_iintrinsic_fast'
checked_intrinsic_ctype(CHECK_OP, OP, name, 64, u##int##64_t) \
~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/keno/julia/src/runtime_intrinsics.c:251:12: note: expanded from macro '\
checked_intrinsic_ctype'
return CHECK_OP(a, b); \
^~~~~~~~~~~~~~
/home/keno/julia/src/runtime_intrinsics.c:885:49: note: expanded from macro 'check_ssub_int'
(b >= 0) ? (a < sTYPEMIN(a) + b) : (a > sTYPEMAX(a) + b)
^~~~~~~~~~~
/home/keno/julia/src/runtime_intrinsics.c:868:23: note: expanded from macro 'sTYPEMAX'
? ~((a - a + ~0) << (8 * sizeof(a) - 1)) \
~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
16 warnings generated.
```
And indeed shifting a negative number to the left is undefined in `C`.
Try an alternative expression for these that hopefully steers clear of any UB.
