BUG: Don't use "=" in cmake variable name
BUG: Don't use "=" in cmake variable name

When testing the flag option "Wformat=2" the '=' character was in the
cmake variable. This causes the test to be run every time cmake is
run.

Change-Id: I028a4c2d9ad4ff88437f1fcfbeeedd26905e11fa

LucasGandel/ITK,PlutoniumHeart/ITK,fbudin69500/ITK,vfonov/ITK,PlutoniumHeart/ITK,spinicist/ITK,blowekamp/ITK,hjmjohnson/ITK,LucasGandel/ITK,vfonov/ITK,malaterre/ITK,fbudin69500/ITK,richardbeare/ITK,BRAINSia/ITK,stnava/ITK,spinicist/ITK,stnava/ITK,thewtex/ITK,hjmjohnson/ITK,LucasGandel/ITK,hjmjohnson/ITK,PlutoniumHeart/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,malaterre/ITK,vfonov/ITK,zachary-williamson/ITK,thewtex/ITK,LucasGandel/ITK,richardbeare/ITK,LucasGandel/ITK,fbudin69500/ITK,hjmjohnson/ITK,spinicist/ITK,Kitware/ITK,Kitware/ITK,blowekamp/ITK,blowekamp/ITK,fbudin69500/ITK,blowekamp/ITK,spinicist/ITK,blowekamp/ITK,stnava/ITK,malaterre/ITK,malaterre/ITK,malaterre/ITK,richardbeare/ITK,BRAINSia/ITK,stnava/ITK,zachary-williamson/ITK,PlutoniumHeart/ITK,Kitware/ITK,fbudin69500/ITK,BRAINSia/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,richardbeare/ITK,zachary-williamson/ITK,spinicist/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,zachary-williamson/ITK,fbudin69500/ITK,thewtex/ITK,blowekamp/ITK,hjmjohnson/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,zachary-williamson/ITK,PlutoniumHeart/ITK,malaterre/ITK,malaterre/ITK,spinicist/ITK,blowekamp/ITK,stnava/ITK,malaterre/ITK,vfonov/ITK,fbudin69500/ITK,BRAINSia/ITK,hjmjohnson/ITK,LucasGandel/ITK,blowekamp/ITK,InsightSoftwareConsortium/ITK,spinicist/ITK,thewtex/ITK,stnava/ITK,zachary-williamson/ITK,InsightSoftwareConsortium/ITK,spinicist/ITK,fbudin69500/ITK,Kitware/ITK,PlutoniumHeart/ITK,thewtex/ITK,richardbeare/ITK,zachary-williamson/ITK,Kitware/ITK,BRAINSia/ITK,spinicist/ITK,PlutoniumHeart/ITK,vfonov/ITK,vfonov/ITK,zachary-williamson/ITK,LucasGandel/ITK,vfonov/ITK,richardbeare/ITK,thewtex/ITK,thewtex/ITK,richardbeare/ITK,PlutoniumHeart/ITK,InsightSoftwareConsortium/ITK,stnava/ITK,Kitware/ITK,zachary-williamson/ITK,stnava/ITK,BRAINSia/ITK,stnava/ITK,hjmjohnson/ITK