Add option cc_wrapper to GN

For example:
cc_wrapper="ccache"
cc_wrapper="icecc"
cc_wrapper="distcc"
cc_wrapper="ccache distcc"

In addition, it deprecates use_ccache and clang_dir.
A user who uses use_ccache must switch to cc_wrapper="ccache"
clang_dir supported icecc in the masquerade way. There is
2 ways to use external compiler wrapper. For example using icecc,
1) CC='icecc gcc'
2) masquerade icecc
 mkdir /opt/icecc/bin
 ln -s /usr/bin/icecc /opt/icecc/bin/gcc
 ln -s /usr/bin/icecc /opt/icecc/bin/g++
 export PATH=/opt/icecc/bin:$PATH
 clang_dir="/opt/icecc/bin/"

This CL uses the chromium#1 way because goma uses the chromium#1 way, and removes
the chromium#2 hack, which is clang_dir.

Review URL: https://codereview.chromium.org/1660053005

Cr-Commit-Position: refs/heads/master@{#377251}

build/config/compiler/BUILD.gn

@@ -6,7 +6,7 @@ import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
-import("//build/toolchain/ccache.gni")
+import("//build/toolchain/cc_wrapper.gni")
 
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
@@ -88,7 +88,7 @@ if (gold_path == false) {
 
 if (use_debug_fission == "default") {
   use_debug_fission = is_debug && !is_win && use_gold &&
-                      linux_use_bundled_binutils && !use_ccache
+                      linux_use_bundled_binutils && cc_wrapper == ""
 }
 
 # default_include_dirs ---------------------------------------------------------

build/toolchain/ccache.gni → build/toolchain/cc_wrapper.gni

@@ -2,11 +2,14 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# Defines the configuration of ccache - a c/c++ compiler cache which can
-# greatly reduce recompilation times.
+# Defines the configuration of cc wrapper
+# ccache: a c/c++ compiler cache which can greatly reduce recompilation times.
+# icecc, distcc: it takes compile jobs from a build and distributes them among
+#                remote machines allowing a parallel build.
 #
-# TIPS:
+# TIPS
 #
+# 1) ccache
 # Set clang_use_chrome_plugins=false if using ccache 3.1.9 or earlier, since
 # these versions don't support -Xclang.  (3.1.10 and later will silently
 # ignore -Xclang, so it doesn't matter if you disable clang_use_chrome_plugins
@@ -18,8 +21,15 @@
 # To avoid -Wparentheses-equality clang warnings, at some cost in terms of
 # speed, you can do:
 # export CCACHE_CPP2=yes
+#
+# 2) icecc
+# Set clang_use_chrome_plugins=false because icecc cannot distribute custom
+# clang libraries.
+#
+# To use icecc and ccache together, set cc_wrapper = "ccache" with
+# export CCACHE_PREFIX=icecc
 
 declare_args() {
-  # Set to true to enable ccache.  Probably doesn't work on windows.
-  use_ccache = false
+  # Set to "ccache", "icecc" or "distcc".  Probably doesn't work on windows.
+  cc_wrapper = ""
 }

build/toolchain/cros/BUILD.gn

@@ -67,5 +67,5 @@ gcc_toolchain("target") {
   toolchain_cpu = target_cpu
   toolchain_os = "linux"
   is_clang = is_clang
-  use_ccache = false
+  cc_wrapper = ""
 }

build/toolchain/gcc_toolchain.gni

@@ -4,7 +4,7 @@
 
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
-import("//build/toolchain/ccache.gni")
+import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ -80,9 +80,10 @@ if (is_cfi) {
 #      default setting.
 #  - is_nacl_glibc
 #      Whether NaCl code is built using Glibc instead of Newlib.
-#  - use_ccache
-#      Override the global use_ccache setting, useful to opt-out of ccache in
-#      a particular toolchain by setting use_ccache = false in it.
+#  - cc_wrapper
+#      Override the global cc_wrapper setting. e.g. "ccache" or "icecc".
+#      useful to opt-out of cc_wrapper in a particular toolchain by setting
+#      cc_wrapper = "" in it.
 #  - use_goma
 #      Override the global use_goma setting, useful to opt-out of goma in a
 #      particular toolchain by setting use_gome = false in it.
@@ -100,17 +101,17 @@ template("gcc_toolchain") {
     assert(defined(invoker.toolchain_os),
            "gcc_toolchain() must specify a \"toolchain_os\"")
 
-    if (defined(invoker.use_ccache)) {
-      use_ccache = invoker.use_ccache
+    if (defined(invoker.cc_wrapper)) {
+      cc_wrapper = invoker.cc_wrapper
     }
     if (defined(invoker.use_goma)) {
       use_goma = invoker.use_goma
     }
     if (use_goma) {
-      assert(!use_ccache, "Goma and ccache can't be used together.")
+      assert(cc_wrapper == "", "Goma and cc_wrapper can't be used together.")
       compiler_prefix = "$goma_dir/gomacc "
-    } else if (use_ccache) {
-      compiler_prefix = "ccache "
+    } else if (cc_wrapper != "") {
+      compiler_prefix = cc_wrapper + " "
     } else {
       compiler_prefix = ""
     }
@@ -425,10 +426,6 @@ template("gcc_toolchain") {
   }
 }
 
-declare_args() {
-  clang_dir = "//third_party/llvm-build/Release+Asserts"
-}
-
 # This is a shorthand for gcc_toolchain instances based on the
 # Chromium-built version of Clang.  Only the toolchain_cpu and
 # toolchain_os variables need to be specified by the invoker, and
@@ -448,7 +445,8 @@ template("clang_toolchain") {
   }
 
   gcc_toolchain(target_name) {
-    prefix = rebase_path(clang_dir + "/bin", root_build_dir)
+    prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
+                         root_build_dir)
     cc = "$prefix/clang"
     cxx = "$prefix/clang++"
     ld = cxx

build/toolchain/linux/BUILD.gn

@@ -81,6 +81,6 @@ gcc_toolchain("mipsel") {
   toolchain_cpu = "mipsel"
   toolchain_os = "linux"
   is_clang = false
-  use_ccache = false
+  cc_wrapper = ""
   use_goma = false
 }

build/toolchain/nacl/BUILD.gn

@@ -54,7 +54,7 @@ template("pnacl_toolchain") {
   # When the compilers are run via goma or ccache rather than directly by
   # GN/Ninja, the goma/ccache wrapper handles .bat files but gets confused
   # by being given the scriptprefix.
-  if (host_os == "win" && !use_goma && !use_ccache) {
+  if (host_os == "win" && !use_goma && cc_wrapper == "") {
     compiler_scriptprefix = scriptprefix
   } else {
     compiler_scriptprefix = ""

docs/ccache_mac.md

@@ -70,7 +70,7 @@ you can also use the absolute path here.)
 You just need to set the use\_ccache variable. Do so like the following:
 
 ```shell
-gn gen out-gn --args='use_ccache=true'
+gn gen out-gn --args='cc_wrapper="ccache"'
 ```
 
 ## Build