Fix default value for LLVM_INCLUDE_DOCS in out of tree build.

llvm-svn: 245790
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 42e4a0e47f04b18940da1fa34cb5822475d4d597
diff --git a/cmake/Modules/HandleOutOfTreeLLVM.cmake b/cmake/Modules/HandleOutOfTreeLLVM.cmake
index 3bf5d60..0e12c88 100644
--- a/cmake/Modules/HandleOutOfTreeLLVM.cmake
+++ b/cmake/Modules/HandleOutOfTreeLLVM.cmake
@@ -77,6 +77,9 @@
   if (NOT DEFINED LLVM_INCLUDE_TESTS)
     set(LLVM_INCLUDE_TESTS ${LLVM_FOUND})
   endif()
+  if (NOT DEFINED LLVM_INCLUDE_DOCS)
+    set(LLVM_INCLUDE_DOCS ${LLVM_FOUND})
+  endif()
   if (NOT DEFINED LLVM_ENABLE_SPHINX)
     set(LLVM_ENABLE_SPHINX OFF)
   endif()