Fix the type of offset that broke 32-bit flang-rt build to use `uint64_t` consistently (#147359)
The recent change of `flang-rt` has code like `std::size_t
offset{offset_};`.
It broke the 32-bit `flang-rt` build because `Component::offset_` is of
type `uint64_t` but `size_t` varies.
Clang complains
```
error: non-constant-expression cannot be narrowed from type 'std::uint64_t' (aka 'unsigned long long') to 'std::size_t' (aka 'unsigned long') in initializer list [-Wc++11-narrowing]
143 | std::size_t offset{offset_};
| ^~~~~~~
```
This patch is to use the consistent `uint64_t` for offset.