[lld] Convert LLVM_CMAKE_PATH to a CMake path

Otherwise I get the following error on windows.
```
CMake Error at D:/bld/lld_1569206597988/work/build/CMakeFiles/CMakeTmp/CMakeLists.txt:2 (set):
  Syntax error in cmake code at

    D:/bld/lld_1569206597988/work/build/CMakeFiles/CMakeTmp/CMakeLists.txt:2

  when parsing string

    D:\bld\lld_1569206597988\_h_env\Library\lib\cmake\llvm

  Invalid character escape '\b'.

CMake Error at D:/bld/lld_1569206597988/_build_env/Library/share/cmake-3.15/Modules/CheckSymbolExists.cmake:100 (try_compile):
  Failed to configure test project build system.
Call Stack (most recent call first):
  D:/bld/lld_1569206597988/_build_env/Library/share/cmake-3.15/Modules/CheckSymbolExists.cmake:57 (__CHECK_SYMBOL_EXISTS_IMPL)
  D:/bld/lld_1569206597988/_h_env/Library/lib/cmake/llvm/HandleLLVMOptions.cmake:943 (check_symbol_exists)
  CMakeLists.txt:56 (include)
```

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D68158

diff --git a/lld/CMakeLists.txt b/lld/CMakeLists.txt
index 53e09f9..48c7081 100644 (file)
--- a/lld/CMakeLists.txt
+++ b/lld/CMakeLists.txt
@@ -35,6 +35,7 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
 
   file(TO_CMAKE_PATH ${LLVM_OBJ_ROOT} LLVM_BINARY_DIR)
+  file(TO_CMAKE_PATH ${LLVM_CMAKE_PATH} LLVM_CMAKE_PATH)
 
   if(NOT EXISTS "${LLVM_CMAKE_PATH}/LLVMConfig.cmake")
     message(FATAL_ERROR "LLVMConfig.cmake not found")