Reduce absolute paths in generated ninja files

mojo/public/tools/bindings/mojom.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # Indicates whether typemapping should be supported in this build
   # configuration. This may be disabled when building external projects which
   # depend on //mojo but which do not need/want all of the Chromium tree
   # dependencies that come with typemapping.
   #
@@ skipping 252 matching lines @@
   if (defined(invoker.sources)) {
     common_generator_args = [
       "--use_bundled_pylibs",
       "generate",
       "{{source}}",
       "-d",
       rebase_path("//", root_build_dir),
       "-I",
       rebase_path("//", root_build_dir),
       "-o",
-      rebase_path(root_gen_dir),
+      rebase_path(root_gen_dir, root_build_dir),
       "--bytecode_path",
-      rebase_path("$root_gen_dir/mojo/public/tools/bindings"),
+      rebase_path("$root_gen_dir/mojo/public/tools/bindings", root_build_dir),
     ]
 
     if (defined(invoker.import_dirs)) {
       foreach(import_dir, invoker.import_dirs) {
         common_generator_args += [
           "-I",
           rebase_path(import_dir, root_build_dir),
         ]
       }
     }
@@ skipping 85 matching lines @@
       script = generate_export_header_script
       outputs = [
         get_path_info(generated_shared_export_header, "abspath"),
       ]
       args = [
         "--export_macro",
         shared_component_export_macro,
         "--impl_macro",
         shared_component_impl_macro,
         "--output_file",
-        generated_shared_export_header,
+        rebase_path(generated_shared_export_header, root_build_dir),
         "--relative_path",
         rebase_path(generated_shared_export_header, root_gen_dir),
       ]
     }
   }
 
   shared_cpp_sources_target_name = "${target_name}_shared_cpp_sources"
   source_set(shared_cpp_sources_target_name) {
     if (defined(invoker.testonly)) {
       testonly = invoker.testonly
@@ skipping 133 matching lines @@
           script = generate_export_header_script
           outputs = [
             get_path_info(generated_export_header, "abspath"),
           ]
           args = [
             "--export_macro",
             "${invoker.component_macro_prefix}${bindings_configuration.component_macro_suffix}_EXPORT",
             "--impl_macro",
             "${invoker.component_macro_prefix}${bindings_configuration.component_macro_suffix}_IMPL",
             "--output_file",
-            generated_export_header,
+            rebase_path(generated_export_header, root_build_dir),
             "--relative_path",
             rebase_path(generated_export_header, root_gen_dir),
           ]
         }
       }
 
       if (!cpp_only) {
         generator_js_outputs =
             [ "{{source_gen_dir}}/{{source_name_part}}.mojom.js" ]
         generator_java_outputs =
@@ skipping 324 matching lines @@
     forward_variables_from(invoker,
                            "*",
                            [
                              "output_prefix",
                              "macro_prefix",
                            ])
     component_output_prefix = invoker.output_prefix
     component_macro_prefix = invoker.macro_prefix
   }
 }