Deps builder: OIIO/OSL/ISPC/OIDN/LLVM/Flex updates

This diff somewhat snowballed out of updating OIDN to 1.4.1 it had some
changes that allowed us to remove the arm hacks we had in place and
revert to using identical versions for a whole bunch of deps. But that
required an update to ISPC which needed a newer LLVM and if we're
updating LLVM we may as well update OSL, and when we update OSL, OIIO
may as well be dragged in soo......anyhow...

This diff updates:

LLVM 9.0.0 (11.0.1 for mac/arm) -> 12.0.0
OIIO 2.1.15.0 -> 2.2.15.1
OSL 1.11.10.0 -> 1.11.14.1
winflex_bison 2.5.5-> 2.5.24 (ispc needed newer bison, windows only dep)
OIDN 1.4.0 -> 1.4.1
ISPC v1.14.1(random hash for mac/arm) -> v1.16.0
Flex 2.6.4 (ISPC needed newer Flex than available on CentOS 7)

and removes most of the "special arm/mac" versions. I think just ssl and
embree are left with special versions.

notable changes:
@LazyDodo included some clang headers in the linux/mac harvest which are
needed to start writing custom clang based tooling like D9465 these were
already shipping on windows, but not the other platforms.

[macOS] Change the `LC_ID_DYLIB` of OpenMP  for {D11997}. This changes
where the executables look for dylibs.

Reviewed By: sebbas, LazyDodo

Differential Revision: https://developer.blender.org/D11748

build_files/build_environment/cmake/osl.cmake

@@ -51,6 +51,7 @@ set(OSL_EXTRA_ARGS
   -DOpenImageIO_ROOT=${LIBDIR}/openimageio/
   -DOSL_BUILD_TESTS=OFF
   -DOSL_BUILD_MATERIALX=OFF
+  -DPNG_ROOT=${LIBDIR}/png
   -DZLIB_LIBRARY=${LIBDIR}/zlib/lib/${ZLIB_LIBRARY}
   -DZLIB_INCLUDE_DIR=${LIBDIR}/zlib/include/
   ${OSL_FLEX_BISON}
@@ -69,13 +70,9 @@ set(OSL_EXTRA_ARGS
   ${OSL_SIMD_FLAGS}
   -Dpugixml_ROOT=${LIBDIR}/pugixml
   -DUSE_PYTHON=OFF
+  -DCMAKE_CXX_STANDARD=14
 )
 
-# Apple arm64 uses LLVM 11, LLVM 10+ requires C++14
-if (APPLE AND "${CMAKE_OSX_ARCHITECTURES}" STREQUAL "arm64")
-  list(APPEND OSL_EXTRA_ARGS -DCMAKE_CXX_STANDARD=14)
-endif()
-
 ExternalProject_Add(external_osl
   URL file://${PACKAGE_DIR}/${OSL_FILE}
   DOWNLOAD_DIR ${DOWNLOAD_DIR}
@@ -93,10 +90,20 @@ add_dependencies(
   ll
   external_openexr
   external_zlib
-  external_flexbison
   external_openimageio
   external_pugixml
 )
+if(WIN32)
+  add_dependencies(
+    external_osl
+    external_flexbison
+  )
+else()
+  add_dependencies(
+    external_osl
+    external_flex
+  )
+endif()
 
 if(WIN32)
   if(BUILD_MODE STREQUAL Release)