message: libpng: update check for VSX enablement
  The deprecated flag ENABLE_VSX should not be used to enable this
  feature. Instead, use the baseline cpu feature set to determine.
diff: @@ -47,7 +47,9 @@ if(";${CPU_BASELINE_FINAL};" MATCHES "SSE2"
  endif()
  if(PPC64LE OR PPC64)
  - if(ENABLE_VSX AND NOT PPC64)
  + # VSX3 features are backwards compatible
  + if(";${CPU_BASELINE_FINAL};" MATCHES "VSX.*"
  + AND NOT PPC64)
  list(APPEND lib_srcs powerpc/powerpc_init.c powerpc/filter_vsx_intrinsics.c)
  add_definitions(-DPNG_POWERPC_VSX_OPT=2)
  else()
  