CMake: Move sphinx detection into AddSphinxTarget.cmake

[beanz]

LGTM!

cmake/config-ix.cmake

if (LLVM_DOXYGEN_EXTERNAL_SEARCH)
       set(LLVM_DOXYGEN_SEARCHENGINE_URL "" CACHE STRING "URL to use for external search.")
       set(LLVM_DOXYGEN_SEARCH_MAPPINGS "" CACHE STRING "Doxygen Search Mappings")
     endif()
   endif()
 else()
   message(STATUS "Doxygen disabled.")
 endif()
 
-if (LLVM_ENABLE_SPHINX)
-  message(STATUS "Sphinx enabled.")
-  find_package(Sphinx REQUIRED)
-  if (LLVM_BUILD_DOCS)
-    add_custom_target(sphinx ALL)
-  endif()
-else()
-  message(STATUS "Sphinx disabled.")
-endif()
-
 set(LLVM_BINDINGS "")
 if(WIN32)
   message(STATUS "Go bindings disabled.")
 else()
   find_program(GO_EXECUTABLE NAMES go DOC "go executable")
   if(GO_EXECUTABLE STREQUAL "GO_EXECUTABLE-NOTFOUND")
     message(STATUS "Go bindings disabled.")
   else()

cmake/modules/AddSphinxTarget.cmake

+
+# Create sphinx target
+if (LLVM_ENABLE_SPHINX AND NOT TARGET sphinx)
+  message(STATUS "Sphinx enabled.")
+  find_package(Sphinx REQUIRED)
+  if (LLVM_BUILD_DOCS)
+    add_custom_target(sphinx ALL)
+  endif()
+else()
+  message(STATUS "Sphinx disabled.")
+endif()
+
+
 # Handy function for creating the different Sphinx targets.
 #
 # ``builder`` should be one of the supported builders used by
 # the sphinx-build command.
 #
 # ``project`` should be the project name
 function (add_sphinx_target builder project)
   set(SPHINX_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/${builder}")

docs/CMakeLists.txt

if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
     install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/doxygen/html/.
       COMPONENT doxygen-html
       DESTINATION "${LLVM_INSTALL_DOXYGEN_HTML_DIR}")
   endif()
 endif()
 endif()
 
 if (LLVM_ENABLE_SPHINX)
-  if (SPHINX_FOUND)
-    include(AddSphinxTarget)
+  if (SPHINX_FOUND)
     if (${SPHINX_OUTPUT_HTML})
       add_sphinx_target(html llvm)
     endif()
 
 
     if (${SPHINX_OUTPUT_MAN})
       add_sphinx_target(man llvm)
     endif()