Enable ARM/linux cross compile to use clang.

build/common.gypi

 # Copyright (c) 2012 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 3685 matching lines @@
                 ],
                 'ldflags': [
                   '-m64',
                 ],
               }],
             ],
           }],
           ['target_arch=="arm"', {
             'target_conditions': [
               ['_toolset=="target"', {
-                'cflags_cc': [
-                  # The codesourcery arm-2009q3 toolchain warns at that the ABI
-                  # has changed whenever it encounters a varargs function. This
-                  # silences those warnings, as they are not helpful and
-                  # clutter legitimate warnings.
-                  '-Wno-abi',
-                ],
                 'conditions': [
+                  ['clang==0', {
+                    'cflags_cc': [
+                      # The codesourcery arm-2009q3 toolchain warns at that the ABI
+                      # has changed whenever it encounters a varargs function. This
+                      # silences those warnings, as they are not helpful and
+                      # clutter legitimate warnings.
+                      '-Wno-abi',
+                    ],
+                  }],
+                  ['clang==1 and arm_arch!=""', {
+                    'cflags': [
+                      '-target arm-linux-gnueabihf',
+                      # TODO(sbc): Remove this once the warning in libvpx is fixed:
+                      # https://code.google.com/p/webm/issues/detail?id=829
+                      '-Wno-absolute-value',

[Nico, 2014/08/08 15:28:44]

nit: Normally, this should go into libvpx.gyp instead. But it looks like it
won't be around for long anyway (that bug's already fixed), so ok.

+                    ],
+                    'ldflags': [
+                      '-target arm-linux-gnueabihf',
+                    ],
+                  }],
                   ['arm_arch!=""', {
                     'cflags': [
                       '-march=<(arm_arch)',
                     ],
                   }],
+                  ['clang==1', {
+                    'cflags': [
+                      # We need to disable clang's builtin assember as it can't
+                      # handle a several of asm files.

[Nico, 2014/08/08 15:28:44]

Include link to http://crbug.com/124610 (the bug title says "android" but it's
really about arm)

+                      '-no-integrated-as',
+                    ],
+                  }],
                   ['arm_tune!=""', {
                     'cflags': [
                       '-mtune=<(arm_tune)',
                     ],
                   }],
                   ['arm_fpu!=""', {
                     'cflags': [
                       '-mfpu=<(arm_fpu)',
                     ],
                   }],
@@ skipping 1951 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',
   },
 }