pangofc-fontmap: Fix check for variable font
FcPatternGetBool()
queries for a given property and returns an
FcResult
to notify whether the property was found and if so (when the
return value is FcResultMatch
), stores the result in the given
argument.
Before this commit, we were passing on the same variable for
both the return value and the out argument. So when a variable font was
encountered, the variable was set to TRUE
by fontconfig, but was then
overwritten with the return value FcResultMatch
which is defined as 0,
aka FALSE
in C.
Fix this by using a different variable for the result and the actual value, and check that both match our expectations.