Allow V8 to be built even when chromium is prebuilt.

When using a prebuilt libwebviewchromium, instead of skipping the entire
directory just include the makefiles needed to build V8 for
external/chromium-libpac to use.

Bug: 17228462
Change-Id: I0f543120265707d47674a85e059787a2c77611bd
(cherry picked from commit ebf434c9a43c7b58acb532e1e22428b931cab44d)
1 file changed