[cmake] Created an aggregate doxygen target for generating doxygen documentation for llvm/all subprojects. Renamed llvm's doxygen generation command to doxygen-llvm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189506 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index 3bf7583..3f57e23 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -465,6 +465,15 @@
 if (LLVM_ENABLE_DOXYGEN)
   message(STATUS "Doxygen enabled.")
   find_package(Doxygen)
+
+  if (DOXYGEN_FOUND)
+    # If we find doxygen and we want to enable doxygen by default create a
+    # global aggregate doxygen target for generating llvm and any/all
+    # subprojects doxygen documentation.
+    if (LLVM_BUILD_DOCS)
+      add_custom_target(doxygen ALL)
+    endif()
+  endif()
 else()
   message(STATUS "Doxygen disabled.")
 endif()