[llvm] Silence warning when compiling with MSVC targetting x86

This fixes:
```
[1614/6998] Building CXX object lib\ExecutionEngine\Orc\CMakeFiles\LLVMOrcJIT.dir\MachOPlatform.cpp.obj
C:\git\llvm-project\llvm\include\llvm/ExecutionEngine/Orc/MachOBuilder.h(367): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
```