tools: switch md5 cmd name based on existence

[dt]

Release note: none.
Epic: none.

[cockroach-teamcity]

This change is 

[rickystewart]

Hmm, just a thought, I think my preferred solution would be to simply check which md5 and fall back to md5sum if it is not available (or vice-versa). The OS doesn't really matter except when it comes to how the two binaries that do the same thing are named. We can simply check whether the binaries are installed. (This is fine, you can still merge it.)

[dt]

TFTR!

simply check which md5

Good point, done.

bors r+

[craig]

Timed out.

[dt]

bors r+

[craig]

Build succeeded:

• linux_arm64_build
• macos_amd64_build
• acceptance
• docker_image_amd64
• unit_tests
• linux_amd64_build
• local_roachtest
• lint
• linux_amd64_fips_build
• local_roachtest_fips
• examples_orms
• windows_build
• check_generated_code
• macos_arm64_build

[dt]

blathers backport 24.1 23.2 23.1

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from 1304f42 to blathers/backport-release-23.1-124293: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.1 failed. See errors above.

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