Enable differential shellcheck #1112

Job	Run time
Docker	8m 27s
Coverage (STP)	28m 27s
clang-format	5m 22s
Coverage (Z3)	32m 7s
macOS	6m 20s
Coverage (Bitwuzla)	33m 14s
Linux (LLVM 14)	12m 59s
Linux (LLVM 13)	12m 26s
Linux (LLVM 12)	12m 28s
Linux (LLVM 11, Doxygen)	13m 7s
Linux (LLVM 10)	12m 34s
Linux (LLVM 9)	12m 8s
Linux (ASan)	44m 26s
Linux (UBSan)	42m 49s
Linux (MSan)	49m 43s
Linux (Z3 only)	11m 38s
Linux (metaSMT)	17m 13s
Linux (STP master)	9m 56s
Linux (Bitwuzla only)	11m 56s
Linux (Latest klee-uclibc)	12m 33s
Linux (Asserts disabled)	12m 13s
Linux (No TCMalloc, optimised runtime)	10m 50s
	6h 52m 56s

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