libpng: zlib flags more elegant (#5656)
libpng: zlib flags more elegant (#5656)


mfherbst/spack,skosukhin/spack,lgarren/spack,EmreAtes/spack,tmerrick1/spack,EmreAtes/spack,skosukhin/spack,EmreAtes/spack,LLNL/spack,tmerrick1/spack,lgarren/spack,mfherbst/spack,krafczyk/spack,skosukhin/spack,lgarren/spack,mfherbst/spack,iulian787/spack,LLNL/spack,krafczyk/spack,LLNL/spack,krafczyk/spack,LLNL/spack,matthiasdiener/spack,krafczyk/spack,tmerrick1/spack,EmreAtes/spack,tmerrick1/spack,lgarren/spack,matthiasdiener/spack,iulian787/spack,krafczyk/spack,iulian787/spack,skosukhin/spack,EmreAtes/spack,lgarren/spack,iulian787/spack,tmerrick1/spack,mfherbst/spack,LLNL/spack,skosukhin/spack,mfherbst/spack,matthiasdiener/spack,matthiasdiener/spack,matthiasdiener/spack,iulian787/spack