Only build against prebuilt sysroot when using 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 76 matching lines @@
 
           # Enable Wayland display server support.
           'enable_wayland_server%' : 0,
 
           # By default we build against a stable sysroot image to avoid
           # depending on the packages installed on the local machine. Set this
           # to 0 to build against locally installed headers and libraries (e.g.
           # if packaging for a linux distro)
           'use_sysroot%': 1,
 
+          # Set this to true when building with Clang.
+          # See http://code.google.com/p/chromium/wiki/Clang for details.
+          # If this is set, clang is used as both host and target compiler in
+          # cross-compile builds.
+          'clang%': 0,
+
           # Override buildtype to select the desired build flavor.
           # Dev - everyday build for development/testing
           # Official - release build (generally implies additional processing)
           # TODO(mmoss) Once 'buildtype' is fully supported (e.g. Windows gyp
           # conversion is done), some of the things which are now controlled by
           # 'branding', such as symbol generation, will need to be refactored
           # based on 'buildtype' (i.e. we don't care about saving symbols for
           # non-Official # builds).
           'buildtype%': 'Dev',
 
@@ skipping 39 matching lines @@
             }, {
               # Default architecture we're building for is the architecture we're
               # building on, and possibly sub-architecture (for iOS builds).
               'target_arch%': '<(host_arch)',
             }],
           ],
         },
         # Copy conditionally-set variables out one scope.
         'chromeos%': '<(chromeos)',
         'chromecast%': '<(chromecast)',
+        'clang%': '<(clang)',
         'desktop_linux%': '<(desktop_linux)',
         'use_aura%': '<(use_aura)',
         'use_ash%': '<(use_ash)',
         'use_cras%': '<(use_cras)',
         'use_ozone%': '<(use_ozone)',
         'embedded%': '<(embedded)',
         'use_libpci%': '<(use_libpci)',
         'use_openssl%': '<(use_openssl)',
         'use_openssl_certs%': '<(use_openssl_certs)',
         'enable_viewport%': '<(enable_viewport)',
@@ skipping 126 matching lines @@
           }],
 
           ['target_arch=="mipsel"', {
             'mips_arch_variant%': 'r1',
           }],
 
           # The system root for linux compiles.
           # Not used when chromecast=1 since ozone_platform_gbm doesn't
           # currently build against the linux sysroot
           # TODO(sbc): http://crbug.com/559708
-          ['OS=="linux" and chromeos==0 and chromecast==0 and use_sysroot==1', {
+          ['OS=="linux" and chromeos==0 and chromecast==0 and clang==1 and use_sysroot==1', {
             # sysroot needs to be an absolute path otherwise it generates
             # incorrect results when passed to pkg-config
             'conditions': [
               ['target_arch=="arm"', {
                 'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_arm-sysroot',
               }],
               ['target_arch=="x64"', {
                 'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_amd64-sysroot',
               }],
               ['target_arch=="ia32"', {
                 'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_i386-sysroot',
               }],
               ['target_arch=="mipsel"', {
                 'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_mips-sysroot',
               }],
             ],
           }, {
             'sysroot%': ''
           }], # OS=="linux" and use_sysroot==1
         ],
       },
 
       # Copy conditionally-set variables out one scope.
       'chromeos%': '<(chromeos)',
       'chromecast%': '<(chromecast)',
+      'clang%': '<(clang)',
       'host_arch%': '<(host_arch)',
       'target_arch%': '<(target_arch)',
       'target_subarch%': '<(target_subarch)',
       'mips_arch_variant%': '<(mips_arch_variant)',
       'mips_dsp_rev%': '<(mips_dsp_rev)',
       'toolkit_views%': '<(toolkit_views)',
       'desktop_linux%': '<(desktop_linux)',
       'use_aura%': '<(use_aura)',
       'use_ash%': '<(use_ash)',
       'use_cras%': '<(use_cras)',
@@ skipping 280 matching lines @@
       # (disabled) in ~/.gyp/include.gypi or via the GYP command line.
       # This setting will override the default.
       #
       # See
       # http://code.google.com/p/chromium/wiki/WindowsPrecompiledHeaders
       # for details.
       'chromium_win_pch%': 0,
 
       # Clang stuff.
       'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
-      # Set this to true when building with Clang.
-      # See http://code.google.com/p/chromium/wiki/Clang for details.
-      # If this is set, clang is used as both host and target compiler in
-      # cross-compile builds.
-      'clang%': 0,
 
       # Use experimental lld linker instead of the platform's default linker.
       'use_lld%': 0,
 
       # Enable plugin installation by default.
       'enable_plugin_installation%': 1,
 
       # Specifies whether to use canvas_skia.cc in place of platform
       # specific implementations of gfx::Canvas. Affects text drawing in the
       # Chrome UI.
@@ skipping 5732 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',
   },
 }