[polly] Fix unused variable warnings
This patch fixes:
polly/lib/Transform/ScheduleOptimizer.cpp:935:17: error: unused
variable 'File' [-Werror,-Wunused-variable]
polly/lib/Transform/ScheduleOptimizer.cpp:936:9: error: unused
variable 'Line' [-Werror,-Wunused-variable]
polly/lib/Transform/ScheduleOptimizer.cpp:937:17: error: unused
variable 'Msg' [-Werror,-Wunused-variable]
