Cmake/deps: Update OSL to 1.11.10.0

This bumps OSL to 1.11.10.0. OSL Has a new build time
dependency: Clang, and more importantly it expects
clang and llvm to share a library folder, which it
previously for us did not.

This patch changes:

-OSL Update to 1.11.10.0

-refactor the llvm/clang/clang-tools-extra builds into the llvm
 build using the llvm-project tarball for building that has all
 of the subprojects in it.

-update ispc/openmp builds since clang no longer its own dependency
 and they have to depend on the llvm build now.

-Update the windows builder to use the 64 bit host tools since it
 ran out of ram linking clang

-Since OSL now needs clang to link successfully a findclang.cmake
 has been provided for linux/OSX

Differential Revision: https://developer.blender.org/D10212

Reviewed By: brecht, sebbas, sybren

CMakeLists.txt

@@ -416,6 +416,7 @@ else()
   option(LLVM_STATIC                  "Link with LLVM static libraries" OFF)
 endif()
 mark_as_advanced(LLVM_STATIC)
+option(WITH_CLANG                   "Use Clang" OFF)
 
 # disable for now, but plan to support on all platforms eventually
 option(WITH_MEM_JEMALLOC   "Enable malloc replacement (http://www.canonware.com/jemalloc)" ON)
@@ -742,6 +743,7 @@ if(WITH_CYCLES)
   # auto enable llvm for cycles_osl
   if(WITH_CYCLES_OSL)
     set(WITH_LLVM ON CACHE BOOL "" FORCE)
+    set(WITH_CLANG ON CACHE BOOL "" FORCE)
   endif()
 else()
   set(WITH_CYCLES_OSL OFF)
@@ -1881,6 +1883,7 @@ if(FIRST_RUN)
   info_cfg_text("Build Options:")
   info_cfg_option(WITH_ALEMBIC)
   info_cfg_option(WITH_BULLET)
+  info_cfg_option(WITH_CLANG)
   info_cfg_option(WITH_CYCLES)
   info_cfg_option(WITH_FFTW3)
   info_cfg_option(WITH_FREESTYLE)