Instrumented libraries: allow overriding CC/CXX.

third_party/instrumented_libraries/instrumented_libraries.gyp

 # 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.
 
 {
   'variables': {
     'verbose_libraries_build%': 0,
     'instrumented_libraries_jobs%': 1,
+    'instrumented_libraries_cc%': '',
+    'instrumented_libraries_cxx%': '',
   },
 
   'libdir': 'lib',
   'ubuntu_release': '<!(lsb_release -cs)',
+  'clang_absolute_path': '<!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang',
+  'clang++_absolute_path': '<!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang++',
 
   'conditions': [
     ['asan==1', {
       'sanitizer_type': 'asan',
     }],
     ['msan==1', {
       'sanitizer_type': 'msan',
     }],
     ['tsan==1', {
       'sanitizer_type': 'tsan',
     }],
     ['use_goma==1', {
-      'cc': '<(gomadir)/gomacc <!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang',
-      'cxx': '<(gomadir)/gomacc <!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang++',
+      'cc': '<(gomadir)/gomacc <(_clang_absolute_path)',
+      'cxx': '<(gomadir)/gomacc <(_clang++_absolute_path)',
     }, {
-      'cc': '<!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang',
-      'cxx': '<!(cd <(DEPTH) && pwd -P)/<(make_clang_dir)/bin/clang++',
+      'cc': '<(clang_absolute_path)',
+      'cxx': '<(clang++_absolute_path)',
+    }],
+    # When building with a custom clang, CC/CXX must be overridden via GYP
+    # variables.
+    ['instrumented_libraries_cc!=""', {
+      'cc': '<(instrumented_libraries_cc)',
+    }],
+    ['instrumented_libraries_cxx!=""', {
+      'cxx': '<(instrumented_libraries_cxx)',
     }],
   ],
 
   'target_defaults': {
     'build_method': 'destdir',
     # Every package must have --disable-static in configure flags to avoid
     # building unnecessary static libs. Ideally we should add it here.
     # Unfortunately, zlib1g doesn't support that flag and for some reason it
     # can't be removed with a GYP exclusion list. So instead we add that flag
     # manually to every package but zlib1g.
@@ skipping 813 matching lines @@
       'extra_configure_flags': [
           '--disable-static',
           # See above.
           '--disable-introspection',
       ],
       'pre_build': 'scripts/pre-build/autoreconf.sh',
       'includes': ['standard_instrumented_package_target.gypi'],
     },
   ],
 }