GetPrerequisites: remove needless variable dereferencing
GetPrerequisites: join if() clauses

These all test the same variable for different values, so only one of them can
ever be true. This also allows to completely remove one variable that only
flagged if one of the conditions matched.
Merge topic 'GetPrerequisites-expansion' into next

d1903de8 GetPrerequisites: join if() clauses
c9e32b0b GetPrerequisites: remove needless variable dereferencing