only build ftcxx tests if BUILD_TESTING
only build ftcxx tests if BUILD_TESTING

kuszmaul/PerconaFT,BohuTANG/ft-index,percona/PerconaFT,kuszmaul/PerconaFT,ottok/PerconaFT,kuszmaul/PerconaFT-tmp,BohuTANG/ft-index,percona/PerconaFT,kuszmaul/PerconaFT-tmp,BohuTANG/ft-index,kuszmaul/PerconaFT,ottok/PerconaFT,percona/PerconaFT,kuszmaul/PerconaFT-tmp,kuszmaul/PerconaFT,BohuTANG/ft-index,kuszmaul/PerconaFT-tmp,ottok/PerconaFT,ottok/PerconaFT,percona/PerconaFT