Add command line flag to avoid overwriting grpc wheels

[allenporter]

grpcio armv7 wheels are broken again, due to this behavior:

• First time a new grpc version exists, its built from source due to --skip_binary=grpc (after Update builder to consider package constraints when skipping binaries (grpc fix) #311 and Add link flags for grpc armv7 wheels (attempt #2) core#63521). Great.
• Second time a build happens (for another package bump) grpc is in the index then grpc is removed from --skip_binary to get it to use an existing wheel, but then it uses the pypi wheel rather than the home assistant index wheel (Missing an option to prioritize --find-links over --index-url pypa/pip#4321). Bad!

To remedy, add a new flag --skip_exists that will remove the local grpc wheel when it already exists in the index before syncing.

This change refactors existing code in check_available_binary to take advantage of its existing test coverage, but it makes the change bigger than to needs to be.

Assuming this direction is good, the rollout steps are:

• Release a new wheel
• Update core to set --skip_exists=grpcio
• Remove the existing 1.43.0 wheel for armv7
• Bump something
• Bump something else again to verify the fix worked.

[pvizeli]

We can remove grpcio from the server to trigger a new build. I personally think that we can merge skip_exists and skip_binary into the same function? Not sure if you ever need one without the other?

[allenporter]

We can remove grpcio from the server to trigger a new build. I personally think that we can merge skip_exists and skip_binary into the same function? Not sure if you ever need one without the other?

It seems like there shouldn't be a correctness problem. My motivation for splitting it were to make it easier to understand (we've overloaded what --skip_binary means compared to pip, but maybe this doesn't make it that much worse). The other motivation was to just be conservative, really about leaving aiohttp alone.

I've updated this to take your suggestion and remove --skip_existing, and always use --skip_binary. 👍🏼

[allenporter]

We can remove grpcio from the server to trigger a new build. I personally think that we can merge skip_exists and skip_binary into the same function? Not sure if you ever need one without the other?

It seems like there shouldn't be a correctness problem. My motivation for splitting it were to make it easier to understand (we've overloaded what --skip_binary means compared to pip, but maybe this doesn't make it that much worse). The other motivation was to just be conservative, really about leaving aiohttp alone.

I've updated this to take your suggestion and remove --skip_existing, and always use --skip_binary. 👍🏼

I think this introduced a problem where --skip_binary is cleared when the second phase runs, so the wheel was clobbered again.