message: adjust default native flags
diff: @@ -41,8 +41,8 @@ option(ENOKI_ENABLE_TESTS "Build Enoki test suite? (Warning, this takes
  if (MSVC)
  if (SKBUILD)
  - # Portable binaries for PyPI
  - set(ENOKI_NATIVE_FLAGS_DEFAULT "")
  + # Reasonably portable binaries for PyPI
  + set(ENOKI_NATIVE_FLAGS_DEFAULT "/arch:AVX")
  else()
  set(ENOKI_NATIVE_FLAGS_DEFAULT "/arch:AVX2")
  endif()
  @@ -50,8 +50,8 @@ elseif (APPLE AND CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
  set(ENOKI_NATIVE_FLAGS_DEFAULT "-mcpu=apple-a12")
  else()
  if (SKBUILD)
  - # Portable binaries for PyPI
  - set(ENOKI_NATIVE_FLAGS_DEFAULT "-march=nehalem")
  + # Reasonably portable binaries for PyPI
  + set(ENOKI_NATIVE_FLAGS_DEFAULT "-march=ivybridge")
  else()
  set(ENOKI_NATIVE_FLAGS_DEFAULT "-march=native")
  endif()
  