Make sure abs-path gn labels have separate target_gen_dirs

tools/gn/function_get_path_info_unittest.cc

Index: tools/gn/function_get_path_info_unittest.cc
diff --git a/tools/gn/function_get_path_info_unittest.cc b/tools/gn/function_get_path_info_unittest.cc
index 306c57e88c134082dc4edca32fe7887b9f6f426b..5a8c4550a3b2c7d6a743bc03279578545cb408a9 100644
--- a/tools/gn/function_get_path_info_unittest.cc
+++ b/tools/gn/function_get_path_info_unittest.cc
@@ -110,6 +110,10 @@ TEST_F(GetPathInfoTest, GenDir) {
   EXPECT_EQ("//out/Debug/gen/src/foo", Call(".", "gen_dir"));
   EXPECT_EQ("//out/Debug/gen/src/foo", Call("bar", "gen_dir"));
   EXPECT_EQ("//out/Debug/gen/foo", Call("//foo/bar.txt", "gen_dir"));
-  // System paths go into the root obj directory.
-  EXPECT_EQ("//out/Debug/gen", Call("/foo/bar.txt", "gen_dir"));
+  // System paths go into the ABS_PATH gen directory
+  EXPECT_EQ("//out/Debug/gen/ABS_PATH/foo", Call("/foo/bar.txt", "gen_dir"));
+#if defined(OS_WIN)
+  EXPECT_EQ("//out/Debug/gen/ABS_PATH/C/foo",
+            Call("/C:/foo/bar.txt", "out_dir"));
+#endif
 }