Rename v8_base, v8_nosnapshot, and mksnapshot to include a suffix of
.<(v8_target_arch). This allows multiple target architectures to be
built in the Android build system, which uses a single shared directory
structure for building host binaries.

BUG=

Review URL: https://codereview.chromium.org/12790011
Patch from Richard Coles <torne@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14209 ce2b1a6d-e550-0410-aec6-3dcde31c8c00