message: march=native flags improvements
diff: @@ -5,7 +5,20 @@ option(ENOKI_ENABLE_JIT "Build Enoki just in time compilation library?" OFF
  option(ENOKI_ENABLE_AUTODIFF "Build Enoki automatic differentation library?" OFF)
  option(ENOKI_ENABLE_PYTHON "Build Python extension library?" OFF)
  option(ENOKI_ENABLE_TESTS "Build Enoki test suite? (Warning, this takes *very* long to compile)" OFF)
  -set(ENOKI_NATIVE_FLAGS "-march=native" CACHE STRING "Compilation flags used to target the host processor architecture.")
  +
  +# Compile for the native processor architecture by default. MSVC cannot detect
  +# this automatically, and the following assumes a reasonably modern CPU with
  +# AVX2 instructions. You may want to overwrite MTS_NATIVE_FLAGS when building
  +# binaries that will be distributed to others.
  +
  +if (MSVC)
  + set(ENOKI_NATIVE_FLAGS_DEFAULT "/arch:AVX2")
  +else()
  + set(ENOKI_NATIVE_FLAGS_DEFAULT "-march=native")
  +endif()
  +
  +set(ENOKI_NATIVE_FLAGS ${ENOKI_NATIVE_FLAGS_DEFAULT} CACHE STRING
  + "Compilation flags used to target the host processor architecture.")
  set(ENOKI_MASTER_PROJECT OFF)
  if (${CMAKE_CURRENT_SOURCE_DIR} STREQUAL ${CMAKE_SOURCE_DIR})
  