When building with debuild inside a chroot, the user's
shell is used by default when running the command with su.
If the user's shell doesn't exist in a default installation the
script fails. Instead of installing a custom user's shell in the
chroot, this commit forces the shell to be bash.
Introduce a StaticAnalysisTool() class to encapsulate the logic needed for
each different static analysis tool and then remove all the copy-pasta'd
code which used to handle these. This should make adding new static
analysis tools as simple as defining a new instance of this object and
adding it to the static_analysis_tools list.
