True, GPS can be jammed. Which just means it won't be available and you cannot fly that approach. As there will be another approach available (at least over here a non precision approach is required as backup for every precision one) that is basicly a non issue. Even if it is an RNAV approach that still can be flown without GPS, DME/DME or DME/VOR is enough for that.
By the way, how hard is it to jam a LOC or GP? Really do not know, but would think they send with quite a bit of power.