[lldb][cmake] Add clang resource dir to LLDB shell tests config

We want to be able to access the Clang resources directory in LLDB shell
tests, this commit adds the ability to do this by adding the
`CLANG_RESOURCE_DIR` CMake variable to the config for LLDB lit tests

Author: chelcassanova

lldb/cmake/modules/LLDBConfig.cmake

@@ -181,6 +181,17 @@ else ()
 endif ()
 include_directories("${CMAKE_CURRENT_BINARY_DIR}/../clang/include")
 
+if(LLDB_BUILT_STANDALONE)
+  if (TARGET clang-resource-headers)
+    get_target_property(CLANG_RESOURCE_DIR clang-resource-headers INTERFACE_INCLUDE_DIRECTORIES)
+    set(CLANG_RESOURCE_DIR "${CLANG_RESOURCE_DIR}/..")
+  else()
+    set(CLANG_RESOURCE_DIR "${LLDB_EXTERNAL_CLANG_RESOURCE_DIR}")
+  endif()
+else()
+  get_clang_resource_dir(CLANG_RESOURCE_DIR PREFIX "${CMAKE_BINARY_DIR}")
+endif()
+
 # GCC silently accepts any -Wno-<foo> option, but warns about those options
 # being unrecognized only if the compilation triggers other warnings to be
 # printed. Therefore, check for whether the compiler supports options in the

lldb/test/Shell/lit.site.cfg.py.in

@@ -35,6 +35,7 @@ config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 # The shell tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-shell")
 config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-shell")
+config.clang_resource_dir = os.path.join("@CLANG_RESOURCE_DIR@")
 
 import lit.llvm
 lit.llvm.initialize(lit_config, config)