[lldb] Fix process pid parsing issue

This patch should fix an issue when parsing the process pid and setting
it in the scripted process.

It can happen that the `crashlog.process_id` attribute is sometimes
parsed as a string. That would cause the scripted process to pick the
default value (0).

To address that, this patch makes sure that the parsed attributed is
converted to the integer type before passing it to the scripted process.

Differential Revision: https://reviews.llvm.org/D151002



Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>