Hook up symbol files to the Windows GN build.

tools/gn/function_toolchain.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/err.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
@@ skipping 142 matching lines @@
     "tool: Specify arguments to a toolchain tool.";
 const char kTool_Help[] =
     "tool: Specify arguments to a toolchain tool.\n"
     "\n"
     "  tool(<command type>) { <command flags> }\n"
     "\n"
     "  Used inside a toolchain definition to define a command to run for a\n"
     "  given file type. See also \"gn help toolchain\".\n"
     "\n"
     "Command types:\n"
+    "\n"
     "  The following values may be passed to the tool() function for the type\n"
     "  of the command:\n"
     "\n"
     "  \"cc\", \"cxx\", \"objc\", \"objcxx\", \"asm\", \"alink\", \"solink\",\n"
     "  \"link\", \"stamp\", \"copy\"\n"
     "\n"
-    "Command flags:\n"
+    "Command flags\n"
     "\n"
     "  These variables may be specified in the { } block after the tool call.\n"
     "  They are passed directly to Ninja. See the ninja documentation for how\n"
     "  they work. Don't forget to backslash-escape $ required by Ninja to\n"
     "  prevent GN from doing variable expansion.\n"
     "\n"
     "    command, depfile, depsformat, description, pool, restat, rspfile,\n"
     "    rspfile_content\n"
     "\n"
     "  (Note that GN uses \"depsformat\" for Ninja's \"deps\" variable to\n"
     "  avoid confusion with dependency lists.)\n"
     "\n"
     "  Additionally, lib_prefix and lib_dir_prefix may be used for the link\n"
     "  tools. These strings will be prepended to the libraries and library\n"
     "  search directories, respectively, because linkers differ on how to\n"
     "  specify them.\n"
     "\n"
     "  Note: On Mac libraries with names ending in \".framework\" will be\n"
     "  added to the link like with a \"-framework\" switch and the lib prefix\n"
     "  will be ignored.\n"
     "\n"
-    "Example:\n"
+    "Ninja variables available to tool invocations\n"
+    "\n"
+    "  When writing tool commands, you use the various built-in Ninja\n"
+    "  variables like \"$in\" and \"$out\" (note that the $ must be escaped\n"
+    "  for it to be passed to Ninja, so write \"\\$in\" in the command\n"
+    "  string).\n"
+    "\n"
+    "  GN defines the following variables for binary targets to access the\n"
+    "  various computed information needed for compiling:\n"
+    "\n"
+    "    - Compiler flags: \"cflags\", \"cflags_c\", \"cflags_cc\",\n"
+    "          \"cflags_objc\", \"cflags_objcc\"\n"
+    "\n"
+    "    - Linker flags: \"ldflags\", \"libs\"\n"
+    "\n"
+    "  GN sets these other variables with target information that can be\n"
+    "  used for computing names for supplimetary files:\n"
+    "\n"
+    "    - \"target_name\": The name of the current target with no\n"
+    "      path information. For example \"mylib\".\n"
+    "\n"
+    "    - \"target_out_dir\": The value of \"target_out_dir\" from the BUILD\n"
+    "      file for this target (see \"gn help target_out_dir\"), relative\n"
+    "      to the root build directory with no trailing slash.\n"
+    "\n"
+    "    - \"root_out_dir\": The value of \"root_out_dir\" from the BUILD\n"
+    "      file for this target (see \"gn help root_out_dir\"), relative\n"
+    "      to the root build directory with no trailing slash.\n"
+    "\n"
+    "Example\n"
+    "\n"
     "  toolchain(\"my_toolchain\") {\n"
     "    # Put these at the top to apply to all tools below.\n"
     "    lib_prefix = \"-l\"\n"
     "    lib_dir_prefix = \"-L\"\n"
     "\n"
     "    tool(\"cc\") {\n"
     "      command = \"gcc \\$in -o \\$out\"\n"
     "      description = \"GCC \\$in\"\n"
     "    }\n"
     "    tool(\"cxx\") {\n"
@@ skipping 129 matching lines @@
     return Value();
 
   Scope::KeyValueMap values;
   block_scope.GetCurrentScopeValues(&values);
   toolchain->args() = values;
 
   return Value();
 }
 
 }  // namespace functions