[CMake] Set LLVM_PATH in the runtimes build

[phosek]

Summary

This avoids using llvm-config for inferring various paths within the
runtimes build. We also set LLVM_INCLUDE_DIR variable that's used by
these builds and move assignment of LLVM_BINARY_DIR and LLVM_LIBRARY_DIR
to the same location for consistency.

[beanz]

Looks reasonable to me.

llvm/trunk/runtimes/CMakeLists.txt

if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
   include(LLVMConfig)
 
   # Setting these variables will allow the sub-build to put their outputs into
   # the library and bin directories of the top-level build.
   set(LLVM_LIBRARY_OUTPUT_INTDIR ${LLVM_LIBRARY_DIR})
   set(LLVM_RUNTIME_OUTPUT_INTDIR ${LLVM_TOOLS_BINARY_DIR})
 
   # This variable makes sure that e.g. llvm-lit is found.
+  set(LLVM_BINARY_DIR ${LLVM_BUILD_BINARY_DIR})
+  set(LLVM_LIBRARY_DIR ${LLVM_BUILD_LIBRARY_DIR})
+  set(LLVM_INCLUDE_DIR ${LLVM_BUILD_MAIN_INCLUDE_DIR})
   set(LLVM_MAIN_SRC_DIR ${LLVM_BUILD_MAIN_SRC_DIR})
   set(LLVM_CMAKE_PATH ${LLVM_MAIN_SRC_DIR}/cmake/modules)
 
+  # This variable is used by individual runtimes to locate LLVM files.
+  set(LLVM_PATH ${LLVM_BUILD_MAIN_SRC_DIR})
+
   if(APPLE)
     set(LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
   endif()
 
   include(CheckLibraryExists)
   include(CheckCCompilerFlag)
 
   # We don't have libc++ (yet).
function(runtime_default_target)
     endif()
 
     llvm_ExternalProject_Add(runtimes
                              ${CMAKE_CURRENT_SOURCE_DIR}
                              DEPENDS ${ARG_DEPENDS} ${CXX_HEADER_TARGET}
                              # Builtins were built separately above
                              CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
                                         -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
-                                        -DLLVM_BINARY_DIR=${LLVM_BINARY_DIR}
-                                        -DLLVM_LIBRARY_DIR=${LLVM_LIBRARY_DIR}
                                         -DLLVM_DEFAULT_TARGET_TRIPLE=${TARGET_TRIPLE}
                                         -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
                                         -DCMAKE_C_COMPILER_TARGET=${TARGET_TRIPLE}
                                         -DCMAKE_CXX_COMPILER_TARGET=${TARGET_TRIPLE}
                                         -DCMAKE_ASM_COMPILER_TARGET=${TARGET_TRIPLE}
                                         -DCMAKE_C_COMPILER_WORKS=ON
                                         -DCMAKE_CXX_COMPILER_WORKS=ON
                                         -DCMAKE_ASM_COMPILER_WORKS=ON
function(runtime_register_target name target)
     endif()
 
     llvm_ExternalProject_Add(runtimes-${name}
                              ${CMAKE_CURRENT_SOURCE_DIR}
                              DEPENDS ${${name}_deps} ${CXX_HEADER_TARGET}
                              # Builtins were built separately above
                              CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
                                         -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
-                                        -DLLVM_BINARY_DIR=${LLVM_BINARY_DIR}
-                                        -DLLVM_LIBRARY_DIR=${LLVM_LIBRARY_DIR}
                                         -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                         -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
                                         -DCMAKE_C_COMPILER_TARGET=${target}
                                         -DCMAKE_CXX_COMPILER_TARGET=${target}
                                         -DCMAKE_ASM_COMPILER_TARGET=${target}
                                         -DCMAKE_C_COMPILER_WORKS=ON
                                         -DCMAKE_CXX_COMPILER_WORKS=ON
                                         -DCMAKE_ASM_COMPILER_WORKS=ON