[CMake] Make bootstrap and compiler-rt depend on cxx-headers.

[ab]

Summary

Since r334468, my understanding is, we no longer always copy the libcxx headers by virtue of their presence when cmake runs.

This is an attempt to make some of the later stages (compiler-rt, and the bootstrapped stages) depend on them being copied, via the cxx-headers target.

[phosek]

LGTM

cfe/trunk/CMakeLists.txt

set(_BOOTSTRAP_DEFAULT_PASSTHROUGH
     LLVM_VERSION_SUFFIX
     LLVM_BINUTILS_INCDIR
     CLANG_REPOSITORY_STRING
     CMAKE_MAKE_PROGRAM
     CMAKE_OSX_ARCHITECTURES
     LLVM_ENABLE_PROJECTS
     LLVM_ENABLE_RUNTIMES)
 
-  # We don't need to depend on compiler-rt if we're building instrumented
+  # We don't need to depend on compiler-rt/libcxx if we're building instrumented
   # because the next stage will use the same compiler used to build this stage.
-  if(TARGET compiler-rt AND NOT LLVM_BUILD_INSTRUMENTED)
+  if(NOT LLVM_BUILD_INSTRUMENTED)
+    if(TARGET compiler-rt)
       add_dependencies(clang-bootstrap-deps compiler-rt)
     endif()
+    if(TARGET cxx-headers)
+      add_dependencies(clang-bootstrap-deps cxx-headers)
+    endif()
+  endif()
 
   set(C_COMPILER "clang")
   set(CXX_COMPILER "clang++")
   if(WIN32)
     set(C_COMPILER "clang-cl.exe")
     set(CXX_COMPILER "clang-cl.exe")
   endif()
 

cfe/trunk/runtime/CMakeLists.txt

if(LLVM_BUILD_EXTERNAL_COMPILER_RT AND EXISTS ${COMPILER_RT_SRC_ROOT}/)
   foreach(variableName ${variableNames})
     if(variableName MATCHES "^COMPILER_RT")
       string(REPLACE ";" "\;" value "${${variableName}}")
       list(APPEND COMPILER_RT_PASSTHROUGH_VARIABLES
         -D${variableName}=${value})
     endif()
   endforeach()
 
+  if(TARGET cxx-headers)
+    set(COMPILER_RT_LIBCXX_DEPENDENCY "cxx-headers")
+  endif()
+
   ExternalProject_Add(compiler-rt
-    DEPENDS llvm-config clang
+    DEPENDS llvm-config clang ${COMPILER_RT_LIBCXX_DEPENDENCY}
     PREFIX ${COMPILER_RT_PREFIX}
     SOURCE_DIR ${COMPILER_RT_SRC_ROOT}
     STAMP_DIR ${STAMP_DIR}
     BINARY_DIR ${BINARY_DIR}
     CMAKE_ARGS ${CLANG_COMPILER_RT_CMAKE_ARGS}
                -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
                -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
                -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}