update MfemCmakeUtilities.cmake so that it searches for PUMI libs with the .dylib suffix (in addition to .a and .so) so that it will find them when PUMI is built with shared libraries on macOS
update MfemCmakeUtilities.cmake so that it searches for PUMI libs with the .dylib suffix (in addition to .a and .so) so that it will find them when PUMI is built with shared libraries on macOS

mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem,mfem/mfem