[gyp] remove unused variables from v8.gyp.

R=machenbach@chromium.org

Change-Id: I9ecd8ef2e34a49b969e3fe38a7daea06ef4b7274
Reviewed-on: https://chromium-review.googlesource.com/895536Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51020}

gypfiles/v8.gyp

@@ -13,9 +13,6 @@
     'v8_experimental_extra_library_files%': [],
     'mksnapshot_exec': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)mksnapshot<(EXECUTABLE_SUFFIX)',
     'v8_os_page_size%': 0,
-    'v8_src': '../src',
-    'v8_include': '../include',
-    'v8_tools': '../tools',
   },
   'includes': ['toolchain.gypi', 'features.gypi', 'inspector.gypi'],
   'targets': [