[LLD][MachO] Fix warning when building with latest MSVC

This fixes:
```
[3902/4335] Building CXX object tools\lld\MachO\CMakeFiles\lldMachO.dir\Arch\X86_64.cpp.obj
C:\git\llvm-project\lld\MachO\Arch\X86_64.cpp(107): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
```

Author: aganea

lld/MachO/Arch/X86_64.cpp

@@ -104,7 +104,7 @@ int64_t X86_64::getEmbeddedAddend(MemoryBufferRef mb, uint64_t offset,
 void X86_64::relocateOne(uint8_t *loc, const Reloc &r, uint64_t value,
                          uint64_t relocVA) const {
   if (r.pcrel) {
-    uint64_t pc = relocVA + (1 << r.length) + pcrelOffset(r.type);
+    uint64_t pc = relocVA + (1ull << r.length) + pcrelOffset(r.type);
     value -= pc;
   }