Fix the variable test condition, wich is used during inclusion of
weston.ini file in the agl and non-agl builds.
Since for non-agl build there is no algprofilegraphics in the
collection, variable expands to an empty string and test condition
evaluates to true for both agl and non-agl builds.
This causes the weston.ini file to be installed regardless of whether
the agl is found or not.
Usage of a different condition check (lenght instead of empty) eliminates
this issue.
