MADchem: DISABLE unity build #1930

Job	Run time
macos-latest: clang++ Release Threads	9m 23s
macos-latest: clang++ Release OneTBB	1m 38s
macos-latest: clang++ Release PaRSEC	1m 36s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	23m 17s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	1m 2s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	1m 8s
macos-latest: clang++ Debug Threads	20m 31s
macos-latest: clang++ Debug OneTBB	1m 43s
macos-latest: clang++ Debug PaRSEC	2m 21s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	47m 56s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	1m 41s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	1m 58s
	1h 54m 14s

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