add ccache support to gn builds

build/toolchain/android/BUILD.gn

 # Copyright 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.
 
 import("//build/config/sysroot.gni")  # Imports android/config.gni.
+import("//build/toolchain/ccache.gni")
 import("//build/toolchain/clang.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/gcc_toolchain.gni")
 
 # The Android GCC toolchains share most of the same parameters, so we have this
 # wrapper around gcc_toolchain to avoid duplication of logic.
 #
 # Parameters:
 #  - android_ndk_sysroot
 #      Sysroot for this architecture.
@@ skipping 13 matching lines @@
     libs_section_prefix = "$android_ndk_lib/crtbegin_dynamic.o"
     libs_section_postfix = "$android_ndk_lib/crtend_android.o"
 
     solink_libs_section_prefix = "$android_ndk_lib/crtbegin_so.o"
     solink_libs_section_postfix = "$android_ndk_lib/crtend_so.o"
 
     # The tools should be run relative to the build dir.
     tool_prefix = rebase_path(invoker.tool_prefix, root_build_dir)
 
     if (use_goma) {
-      goma_prefix = "$goma_dir/gomacc "
+      assert(!use_ccache, "Goma and ccache can't be used together.")
+      compiler_prefix = "$goma_dir/gomacc "
+    } else if (use_ccache) {
+      compiler_prefix = "ccache "
     } else {
-      goma_prefix = ""
+      compiler_prefix = ""
     }
 
-    cc = goma_prefix + tool_prefix + "gcc"
-    cxx = goma_prefix + tool_prefix + "g++"
+    cc = compiler_prefix + tool_prefix + "gcc"
+    cxx = compiler_prefix + tool_prefix + "g++"
     ar = tool_prefix + "ar"
     ld = cxx
 
     toolchain_os = "android"
     toolchain_cpu_arch = invoker.toolchain_cpu_arch
 
     # We make the assumption that the gcc_toolchain will produce a soname with
     # the following definition.
     soname = "{{target_output_name}}{{output_extension}}"
 
@@ skipping 35 matching lines @@
   toolchain_cpu_arch = "arm"
 }
 
 android_gcc_toolchain("mipsel") {
   android_ndk_sysroot = "$android_ndk_root/$mips_android_sysroot_subdir"
   android_ndk_lib_dir = "usr/lib"
 
   tool_prefix = "$mips_android_toolchain_root/bin/mipsel-linux-android-"
   toolchain_cpu_arch = "mipsel"
 }