llvm_tools: Fix manifest update

Usually we don't need the manifest update with llvm-next
because pgo is not default there.

Remove default manifest packages from llvm-next.
Add unit test for main.

BUG=None
TEST=unit test

Change-Id: I1ef78be8184985e047db8ae68eda2f01c989a7a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/3932864
Tested-by: Denis Nikitin <denik@chromium.org>
Commit-Queue: Denis Nikitin <denik@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
2 files changed