Better dune support #59

Job	Run time
Coq integration tests (8.4, 3.6)	48s
Coq integration tests (8.5, 3.6)	1m 1s
Coq integration tests (8.6, 3.6)	1m 2s
Coq integration tests (8.7, 3.6)	48s
Coq integration tests (8.8, 3.6)	51s
Coq integration tests (8.9, 3.6)	48s
Coq integration tests (8.10, 3.6)	58s
Coq integration tests (8.11, 3.6)	54s
Coq integration tests (8.12, 3.6)	58s
Coq integration tests (8.13, 3.6)	50s
Coq integration tests (8.14, 3.6)	58s
Coq integration tests (8.15, 3.6)	56s
Coq integration tests (8.16, 3.6)	1m 1s
Coq integration tests (8.17, 3.6)	56s
Coq integration tests (8.18, 3.6)	1m 12s
Coq integration tests (8.19, 3.6)	1m 6s
Coq integration tests (master, 3.6)	4m 5s
	19m 12s

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