[lldb] Force override when adding crashlog command

When using interactive crashlog from an IDE, it can happen that the user
already have the `command script import lldb.macosx.crashlog` command on
their `lldbinit` file.

That leads to showing some message:

```
error: cannot add command: user command exists and force replace not set
error: cannot add command: user command exists and force replace not set
```

This leads to confusion because the crashlog symbolication continues and
succeeds even after these errors.

To address that, the crashlog commands get overridden everytime the
script get re-imported.

rdar://103403943

Differential Revision: https://reviews.llvm.org/D140113



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>