Refine selftest further #498

Job	Run time
examples_ntt_kyber_dilithium_neon_core	22m 31s
Dry Run (slothy.targets.arm_v7m.cortex_m7)	39s
examples_ntt_kyber_dilithium_helium_core	2m 24s
examples_basic	37s
Dry Run (slothy.targets.arm_v81m.cortex_m55r1)	3m 16s
fft	6m 29s
Dry Run (slothy.targets.arm_v81m.cortex_m85r1)	2m 57s
Dry Run (slothy.targets.aarch64.cortex_a55)	9m 5s
sqmag	54s
tutorial	20m 10s
Dry Run (slothy.targets.aarch64.cortex_a72_frontend)	39m 18s
Dry Run (slothy.targets.aarch64.apple_m1_firestorm_experimental)	28m 54s
Dry Run (slothy.targets.aarch64.apple_m1_icestorm_experimental)	23m 24s
	2h 40m 38s

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