[lldb][cmake] Populate Clang resource dir for CMakeCache

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

Author: chelcassanova

lldb/cmake/modules/LLDBFramework.cmake

@@ -121,7 +121,7 @@ add_custom_command(TARGET liblldb POST_BUILD
 if(NOT APPLE_EMBEDDED)
   if (TARGET clang-resource-headers)
     add_dependencies(liblldb clang-resource-headers)
-    set(clang_resource_headers_dir $<TARGET_PROPERTY:clang-resource-headers,INTERFACE_INCLUDE_DIRECTORIES>)
+    get_target_property(clang_resource_headers_dir clang-resource-headers INTERFACE_INCLUDE_DIRECTORIES)
   else()
     set(clang_resource_headers_dir ${LLDB_EXTERNAL_CLANG_RESOURCE_DIR}/include)
     if(NOT EXISTS ${clang_resource_headers_dir})
@@ -135,6 +135,8 @@ if(NOT APPLE_EMBEDDED)
             $<TARGET_FILE_DIR:liblldb>/Resources/Clang/include
     COMMENT "LLDB.framework: copy clang vendor-specific headers"
   )
+
+  set(CLANG_RESOURCE_DIR ${clang_resource_headers_dir} CACHE FILEPATH "")
 endif()
 
 # Add an rpath pointing to the directory where LLDB.framework is installed.

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)