CMake/OpenSubdiv: Rename INCLUDE_DIR -> INCLUDE_DIRS.

Ref {D8855}

Unix and Apple platform files use find_package(OpenSubdiv) which sets
`OPENSUBDIV_INCLUDE_DIR` as an advanced variable, as well as
`OPENSUBDIV_INCLUDE_DIRS` which should be used usually.
Windows sets `OPENSUBDIV_INCLUDE_DIR` which is used by the rest
of the code.

This patch renames it to `_DIRS` everywhere, for it to be like other
similar variables.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D8917

build_files/cmake/platform/platform_win32.cmake

@@ -565,7 +565,7 @@ if(WITH_IMAGE_OPENJPEG)
 endif()
 
 if(WITH_OPENSUBDIV)
-  set(OPENSUBDIV_INCLUDE_DIR ${LIBDIR}/opensubdiv/include)
+  set(OPENSUBDIV_INCLUDE_DIRS ${LIBDIR}/opensubdiv/include)
   set(OPENSUBDIV_LIBPATH ${LIBDIR}/opensubdiv/lib)
   set(OPENSUBDIV_LIBRARIES
     optimized ${OPENSUBDIV_LIBPATH}/osdCPU.lib

intern/cycles/CMakeLists.txt

@@ -274,7 +274,7 @@ if(WITH_OPENSUBDIV)
   add_definitions(-DWITH_OPENSUBDIV)
   include_directories(
     SYSTEM
-    ${OPENSUBDIV_INCLUDE_DIR}
+    ${OPENSUBDIV_INCLUDE_DIRS}
   )
 endif()
 

intern/opensubdiv/CMakeLists.txt

@@ -45,7 +45,7 @@ if(WITH_OPENSUBDIV)
   endmacro()
 
   list(APPEND INC_SYS
-    ${OPENSUBDIV_INCLUDE_DIR}
+    ${OPENSUBDIV_INCLUDE_DIRS}
     ${GLEW_INCLUDE_PATH}
   )