flamenco, fuzz: add stubbed binaries to CI for CPI test vectors #1971

Job	Run time
clusterfuzz / ARfuzz-publish (linux_clang_haswell)	5m 56s
clusterfuzz / solfuzz-build-and-publish	7m 31s
book / build	28s
book / Deploy	10s
trigger	1s
	14m 6s

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