[llvm] [BOLT] Fix pwrite assertion failure when patching .dynsym at high offsets (PR #198569)

[Jinjie Huang via llvm-commits]

Jinjie-Huang wrote:

Since most `pwrite` usages in BOLT come from `raw_fd_ostream` (which inherits from `raw_pwrite_stream`). Therefore, it seems quite convenient to introduce a `pwrite` wrapper to unify the `pwrite` calls across BOLT.

https://github.com/llvm/llvm-project/pull/198569