Fixes for misnamed toolchain from https://github.com/appcelerator/v8_titanium.

Added a way to specify the NDK path since the Mac versions of the NDK aren't checked into the tools repo.

Disabled a few dependencies which do not build on the Mac but which aren't needed for building usable V8 static libraries.

Made the including of libdl and librt omitted for Mac hosted builds.

BUG=

Review URL: https://codereview.chromium.org/1879793002

Cr-Commit-Position: refs/heads/master@{#35456}