[build] Use MSVS 2015 by default.

src/base.isolate

 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 {
   'includes': [
     '../third_party/icu/icu.isolate',
+
+    # MSVS runtime libraries.
+    '../gypfiles/win/msvs_dependencies.isolate',
   ],
   'conditions': [
     ['v8_use_snapshot=="true" and v8_use_external_startup_data==1', {
       'variables': {
         'files': [
           '<(PRODUCT_DIR)/natives_blob.bin',
           '<(PRODUCT_DIR)/snapshot_blob.bin',
         ],
       },
     }],
@@ skipping 18 matching lines @@
           '../third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer<(EXECUTABLE_SUFFIX)',
         ],
       },
     }],
     # Workaround for https://code.google.com/p/swarming/issues/detail?id=211
     ['asan==0 or cfi_vptr==0 or msan==0 or tsan==0', {
       'variables': {},
     }],
   ],
 }