* commiting to let marc investigate

* quick hack/fix

* switching windows arch to x86_64

* xpp: partial halide build fixes

* xpp: fix macOS halide generator include directories

* xpp: upgrade to halide_buffer_t type

* xpp: continue halide upgrade

* xpp: prepare migration to newer buffer type

* xpp: migrate halide to new buffer type

* xpp: more cmake cleanup

* xpp: fix generator compilation flags

* xpp: add USE_CONAN cmake option

* xpp: switch to clang 6.0.1