[llvm] [Bazel] Support opt-driver library, like clang-driver (PR #79205)

[William Moses via llvm-commits]

wsmoses wrote:

@efriedma-quic @MaskRay when I did the build matrix of options unfortunately the `DBUILD_SHARED_LIBS` one kept running into issues, so I refactored the opt library in the way shown for all of CI to succeed.

@efriedma-quic note, since I had to make a separate driver function, I made it future compatible for https://github.com/llvm/llvm-project/pull/79227. Once this lands, I will rebase the new test/driver in that PR on this.

https://github.com/llvm/llvm-project/pull/79205