Add support for single-CU build #3748

Job	Run time
Linting (ubuntu-latest)	44s
Examples (macos-latest)	7s
Quickcheck (aarch64)	49s
Examples (ubuntu-latest)	4s
lint-markdown-link	33s
Quickcheck (x86_64)	44s
Quickcheck C90 (aarch64)	1s
Quickcheck C90 (x86_64)	43s
Quickcheck lib (macos-latest)	12s
Quickcheck windows-latest	29s
Quickcheck lib (ubuntu-latest)	31s
Functional tests (${{ matrix.target.arch }}${{ (((matrix.target.mode != 'native') && ', cross') \|\| '') }})	1s
Compiler tests (${{ matrix.target.name }})	1s
Non-standard configurations	1s
Platform tests (${{ matrix.target.name }})	1s
CBMC (ML-KEM-512)	1s
CBMC (ML-KEM-768)	1s
CBMC (ML-KEM-1024)	1s
Compatibility tests (${{ matrix.container.id }})	1s
Compatibility tests (${{ matrix.container.id }})	1s
	5m 6s

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