Try again to get tests passing again on Windows.

Things pass locally, but some tests on some bots are still unhappy.
I'm not sure why. See if using forward slashes as before helps.

clang/test/Unit/lit.site.cfg.py.in

@@ -2,14 +2,14 @@
 
 import sys
 
-config.llvm_src_root = path(r"@LLVM_SOURCE_DIR@")
-config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
-config.llvm_tools_dir = path(r"@LLVM_TOOLS_DIR@")
-config.llvm_libs_dir = path(r"@LLVM_LIBS_DIR@")
+config.llvm_src_root = path("@LLVM_SOURCE_DIR@")
+config.llvm_obj_root = path("@LLVM_BINARY_DIR@")
+config.llvm_tools_dir = path("@LLVM_TOOLS_DIR@")
+config.llvm_libs_dir = path("@LLVM_LIBS_DIR@")
 config.llvm_build_mode = "@LLVM_BUILD_MODE@"
-config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
+config.clang_obj_root = path("@CLANG_BINARY_DIR@")
 config.enable_shared = @ENABLE_SHARED@
-config.shlibdir = path(r"@SHLIBDIR@")
+config.shlibdir = path("@SHLIBDIR@")
 config.target_triple = "@TARGET_TRIPLE@"
 
 # Support substitution of the tools_dir, libs_dirs, and build_mode with user
@@ -26,4 +26,4 @@ except KeyError:
 
 # Let the main config do the real work.
 lit_config.load_config(
-    config, os.path.join(path(r"@CLANG_SOURCE_DIR@"), "test/Unit/lit.cfg.py"))
+    config, os.path.join(path("@CLANG_SOURCE_DIR@"), "test/Unit/lit.cfg.py"))

clang/test/lit.site.cfg.py.in

@@ -2,16 +2,16 @@
 
 import sys
 
-config.llvm_src_root = path(r"@LLVM_SOURCE_DIR@")
-config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
-config.llvm_tools_dir = path(r"@LLVM_TOOLS_DIR@")
-config.llvm_libs_dir = path(r"@LLVM_LIBS_DIR@")
-config.llvm_shlib_dir = path(r"@SHLIBDIR@")
+config.llvm_src_root = path("@LLVM_SOURCE_DIR@")
+config.llvm_obj_root = path("@LLVM_BINARY_DIR@")
+config.llvm_tools_dir = path("@LLVM_TOOLS_DIR@")
+config.llvm_libs_dir = path("@LLVM_LIBS_DIR@")
+config.llvm_shlib_dir = path("@SHLIBDIR@")
 config.llvm_plugin_ext = "@LLVM_PLUGIN_EXT@"
-config.lit_tools_dir = path(r"@LLVM_LIT_TOOLS_DIR@")
-config.clang_obj_root = path(r"@CLANG_BINARY_DIR@")
-config.clang_src_dir = path(r"@CLANG_SOURCE_DIR@")
-config.clang_tools_dir = path(r"@CLANG_TOOLS_DIR@")
+config.lit_tools_dir = path("@LLVM_LIT_TOOLS_DIR@")
+config.clang_obj_root = path("@CLANG_BINARY_DIR@")
+config.clang_src_dir = path("@CLANG_SOURCE_DIR@")
+config.clang_tools_dir = path("@CLANG_TOOLS_DIR@")
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.host_cxx = "@CMAKE_CXX_COMPILER@"

llvm/cmake/modules/AddLLVM.cmake

@@ -1486,7 +1486,7 @@ function(configure_lit_site_cfg site_in site_out)
     string(REPLACE ";" "\\;" ARG_PATH_VALUES_ESCAPED "${ARG_PATH_VALUES}")
     get_filename_component(OUTPUT_DIR ${site_out} DIRECTORY)
     execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
-      "import os, sys; sys.stdout.write(';'.join(os.path.relpath(p, sys.argv[1]) if p else '' for p in sys.argv[2].split(';')))"
+      "import os, sys; sys.stdout.write(';'.join(os.path.relpath(p, sys.argv[1]).replace('\\\\', '/') if p else '' for p in sys.argv[2].split(';')))"
       ${OUTPUT_DIR}
       ${ARG_PATH_VALUES_ESCAPED}
       OUTPUT_VARIABLE ARG_PATH_VALUES_RELATIVE)

llvm/test/Unit/lit.site.cfg.py.in

@@ -2,12 +2,12 @@
 
 import sys
 
-config.llvm_src_root = path(r"@LLVM_SOURCE_DIR@")
-config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
-config.llvm_tools_dir = path(r"@LLVM_TOOLS_DIR@")
+config.llvm_src_root = path("@LLVM_SOURCE_DIR@")
+config.llvm_obj_root = path("@LLVM_BINARY_DIR@")
+config.llvm_tools_dir = path("@LLVM_TOOLS_DIR@")
 config.llvm_build_mode = "@LLVM_BUILD_MODE@"
 config.enable_shared = @ENABLE_SHARED@
-config.shlibdir = path(r"@SHLIBDIR@")
+config.shlibdir = path("@SHLIBDIR@")
 
 # Support substitution of the tools_dir and build_mode with user parameters.
 # This is used when we can't determine the tool dir at configuration time.

llvm/test/lit.site.cfg.py.in

@@ -4,14 +4,14 @@ import sys
 
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
-config.llvm_src_root = path(r"@LLVM_SOURCE_DIR@")
-config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
-config.llvm_tools_dir = path(r"@LLVM_TOOLS_DIR@")
-config.llvm_lib_dir = path(r"@LLVM_LIBRARY_DIR@")
-config.llvm_shlib_dir = path(r"@SHLIBDIR@")
+config.llvm_src_root = path("@LLVM_SOURCE_DIR@")
+config.llvm_obj_root = path("@LLVM_BINARY_DIR@")
+config.llvm_tools_dir = path("@LLVM_TOOLS_DIR@")
+config.llvm_lib_dir = path("@LLVM_LIBRARY_DIR@")
+config.llvm_shlib_dir = path("@SHLIBDIR@")
 config.llvm_shlib_ext = "@SHLIBEXT@"
 config.llvm_exe_ext = "@EXEEXT@"
-config.lit_tools_dir = path(r"@LLVM_LIT_TOOLS_DIR@")
+config.lit_tools_dir = path("@LLVM_LIT_TOOLS_DIR@")
 config.python_executable = "@PYTHON_EXECUTABLE@"
 config.gold_executable = "@GOLD_EXECUTABLE@"
 config.ld64_executable = "@LD64_EXECUTABLE@"