macOS Fixes / Larger Build Matrix

[promiseofcake]

• feat: Expand build matrix to include newer Bazel Versions:
  • Include all Bazel releases from 0.9.0 - 0.13.0
  • Skip OSX Failures on Bazel < 0.12.0 (see https://github.com/bazelbuild/bazel/issues/4794)
• fix: Incorporate OSX fix from bazelbuild/bazel tools/cpp/osx_cc_wrapper.sh@f98a7a2f
  • Also includes /usr/bin to the clang search path to access the linker in Bazel 0.12+
  • Caveat: The macOS build is less hermetic, and relies on system binutils and libraries.
• fix: removal of cc_inc_library
• fix: Fixes #11 by removing libunwind for now

This will fail for OSX builds with Bazel <= 0.12.0, I am not sure that statically linking gtest is the correct approach here to because this issue has a greater scope in other projects.

Internal ref: ML-1330

[promiseofcake]

~3764b99 replaces the -B/usr/bin argument to clang and specifying a search path of tools/cpp/tool_wrappers/mac which has a symlink to /usr/bin/ld to reduce the unintended consequences of including the larger scoped path.~

Reverting 3764b99 due to it's inability to be utilized by other workspaces. This ld workaround might be overkill and might swap back to including all of /usr/bin in the search path since prior to Bazel 0.13.0, the user's entire PATH was leveraged for our Darwin builds, so I don't see this as a huge regression.