clang: Enable using a different compiler path for standalone webkit make builds.

build/common.gypi

 # Copyright (c) 2011 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 471 matching lines @@
     # This is the location of the sandbox binary. Chrome looks for this before
     # running the zygote process. If found, and SUID, it will be used to
     # sandbox the zygote process and, thus, all renderer processes.
     'linux_sandbox_path%': '',
 
     # Set this to true to enable SELinux support.
     'selinux%': 0,
 
     # Set this to true when building with Clang.
     # See http://code.google.com/p/chromium/wiki/Clang for details.
-    # TODO: eventually clang should behave identically to gcc, and this
-    # won't be necessary.
     'clang%': 0,
+    'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
 
     # These two variables can be set in GYP_DEFINES while running
     # |gclient runhooks| to let clang run a plugin in every compilation.
     # Only has an effect if 'clang=1' is in GYP_DEFINES as well.
     # Example:
     #     GYP_DEFINES='clang=1 clang_load=/abs/path/to/libPrintFunctionNames.dylib clang_add_plugin=print-fns' gclient runhooks
 
     'clang_load%': '',
     'clang_add_plugin%': '',
 
@@ skipping 2025 matching lines @@
     }],
     ['enable_new_npdevice_api==1', {
       'target_defaults': {
         'defines': [
           'ENABLE_NEW_NPDEVICE_API',
         ],
       },
     }],
     ['clang==1', {
       'make_global_settings': [
-        ['CC', 'third_party/llvm-build/Release+Asserts/bin/clang'],
-        ['CXX', 'third_party/llvm-build/Release+Asserts/bin/clang++'],
+        ['CC', '<(make_clang_dir)/bin/clang'],
+        ['CXX', '<(make_clang_dir)/bin/clang++'],
         ['LINK', '$(CXX)'],
         ['CC.host', '$(CC)'],
         ['CXX.host', '$(CXX)'],
         ['LINK.host', '$(LINK)'],
       ],
     }],
   ],
   'xcode_settings': {
     # DON'T ADD ANYTHING NEW TO THIS BLOCK UNLESS YOU REALLY REALLY NEED IT!
     # This block adds *project-wide* configuration settings to each project
@@ skipping 13 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }