cotire can't handle generated files in llvm

[Trass3r]

Tried this on the llvm project with ninja generator on Win7.

Index: cmake/modules/AddLLVM.cmake
===================================================================
--- cmake/modules/AddLLVM.cmake	(revision 292100)
+++ cmake/modules/AddLLVM.cmake	(working copy)
@@ -547,6 +547,8 @@
   if(ARG_SHARED OR ARG_MODULE)
     llvm_externalize_debuginfo(${name})
   endif()
+
+  cotire(${name})
 endfunction()
 
 macro(add_llvm_library name)
Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt	(revision 292100)
+++ CMakeLists.txt	(working copy)
@@ -800,6 +800,7 @@
   endif()
 endif()
 
+include(Cotire)
 include(AddLLVM)
 include(TableGen)
 

When running ninja all_pch it chokes on the X macro like code below:

*CXX_prefix.hxx.log:

include/llvm/IR/Attributes.h(71): fatal error C1083: Cannot open include file: 'llvm/IR/Attributes.gen': No such file or directory

enum AttrKind {
    // IR-Level Attributes
    None,                  ///< No attributes have been set
    #define GET_ATTR_ENUM
    #include "llvm/IR/Attributes.gen"