cmake: tweaks for vtools trunk-based development

[ivotron]

Needs to be merged after main is made the default branch in vtools, so that builds work with the new trunk-based development model in vtools.

Backports Required

• [x] none - not a bug fix
• [ ] none - this is a backport
• [ ] none - issue does not exist in previous branches
• [ ] none - papercut/not impactful enough to backport
• [ ] v24.1.x
• [ ] v23.3.x
• [ ] v23.2.x

Release Notes

• none

[vbotbuildovich]

new failures in https://buildkite.com/redpanda/redpanda-dev/builds/102#01911742-b617-41e4-b2af-0ae716675ef9:

"rptest.tests.nodes_decommissioning_test.NodesDecommissioningTest.test_recycle_all_nodes.auto_assign_node_id=True"

new failures in https://buildkite.com/redpanda/redpanda-dev/builds/109#0191257c-aa95-491e-92eb-8af834344e14:

"rptest.tests.partition_force_reconfiguration_test.PartitionForceReconfigurationTest.test_basic_reconfiguration.acks=-1.restart=True.controller_snapshots=False"

[vbotbuildovich]

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/109#0191257c-aa97-46b6-aa99-9823908de6e2

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/109#0191257e-0700-42be-aa11-8525d4d2a7be

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/116#019125dd-2627-4b26-9f7f-f7c186bb456a

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/116#019125dd-7e37-4b05-abdd-0fd42f764ef5

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/116#019125dd-7e3a-4860-8325-8285089152b4

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/116#019125dd-7e35-4345-8e87-19df93d866d2

ducktape was retried in https://buildkite.com/redpanda/redpanda-dev/builds/116#019128c1-e635-4eda-b094-2db7042d5be2

[ivotron]

build that tests these changes is in https://buildkite.com/redpanda/redpanda-dev/builds/116. It's passing except from some flaky tests in ducktape that are irrelevant to the changes in this PR. The bk-redpanda build can be ignored for now since that is using dev but we want to use main

[ivotron]

the jobs are all running on the redpanda pipeline. They're the same that already passed in the redpanda-dev pipeline, so I'm confident they'll pass OK. I'll force-merge to avoid having PRs and schedules that run on tip of dev fail.