[lldb] Avoid build warnings when building for Windows. NFC. (#159345)
This avoids the following warnings from Clang:
../../lldb/source/Host/windows/Host.cpp:324:3: warning: default label in switch which covers all enumeration values [-Wcovered-switch-default]
324 | default:
| ^
../../lldb/source/Host/common/File.cpp:662:26: warning: cast from 'const void *' to 'char *' drops const qualifier [-Wcast-qual]
662 | .write((char *)buf, num_bytes);
| ^