Hide clang-wpa executable behind a CMake variable so it won't be built by default

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82751 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index 74a810c..91039e0 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -1,4 +1,7 @@
 add_subdirectory(clang-cc)
 add_subdirectory(driver)
 add_subdirectory(index-test)
-add_subdirectory(wpa)
+option(CLANG_BUILD_EXPERIMENTAL "Build experimenal Clang tools" OFF)
+if (CLANG_BUILD_EXPERIMENTAL)
+  add_subdirectory(wpa)
+endif ()