Piz Daint: Fix Detection Modern CMake

Fix detection of PNGwriter and Splash on Piz Daint with modern
CMake.

Author: ax3l

etc/picongpu/pizdaint-cscs/picongpu.profile.example

@@ -52,17 +52,17 @@ export BOOST_ROOT=$SCRATCH/lib/boost-1.62.0
 export ZLIB_ROOT=$SCRATCH/lib/zlib-1.2.11
 export PNG_ROOT=$SCRATCH/lib/libpng-1.6.34
 export BLOSC_ROOT=$SCRATCH/lib/blosc-1.12.1
-export PNGWRITER_ROOT=$SCRATCH/lib/pngwriter-0.7.0
+export PNGwriter_DIR=$SCRATCH/lib/pngwriter-0.7.0
 export ADIOS_ROOT=$SCRATCH/lib/adios-1.13.0
-export SPLASH_ROOT=$SCRATCH/lib/splash-1.7.0
+export Splash_DIR=$SCRATCH/lib/splash-1.7.0
 
 export LD_LIBRARY_PATH=$BOOST_ROOT/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH=$ZLIB_ROOT/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH=$PNG_ROOT/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH=$BLOSC_ROOT/lib:$LD_LIBRARY_PATH
-export LD_LIBRARY_PATH=$PNGWRITER_ROOT/lib:$LD_LIBRARY_PATH
+export LD_LIBRARY_PATH=$PNGwriter_DIR/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH=$ADIOS_ROOT/lib:$LD_LIBRARY_PATH
-export LD_LIBRARY_PATH=$SPLASH_ROOT/lib:$LD_LIBRARY_PATH
+export LD_LIBRARY_PATH=$Splash_DIR/lib:$LD_LIBRARY_PATH
 
 export PATH=$PNG_ROOT/bin:$PATH
 export PATH=$ADIOS_ROOT/bin:$PATH