Allow main function executable in cairo-run #6066

Job	Run time
check-website	9s
scarb-metadata compatibility check	38s
build test linux x86-64	3m 32s
check-rust	4m 26s
build test windows x86-64	7m 59s
doc tests	3m 2s
test linux x86-64 1/8	9m 6s
test linux x86-64 2/8	11m 58s
test linux x86-64 3/8	13m 25s
test linux x86-64 4/8	8m 22s
test linux x86-64 5/8	8m 17s
test linux x86-64 6/8	6m 43s
test linux x86-64 7/8	6m 29s
test linux x86-64 8/8	4m 18s
test windows x86-64 1/8	8m 36s
test windows x86-64 2/8	12m 4s
test windows x86-64 3/8	11m 29s
test windows x86-64 4/8	8m 32s
test windows x86-64 5/8	9m 12s
test windows x86-64 6/8	5m 56s
test windows x86-64 7/8	6m 2s
test windows x86-64 8/8	5m 5s
	2h 35m 20s

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