Allow main function executable in cairo-run #6072

Job	Run time
check-rust	3m 48s
check-website	9s
build test linux x86-64	3m 21s
scarb-metadata compatibility check	38s
build test windows x86-64	9m 48s
doc tests	3m 10s
test linux x86-64 1/8	9m 25s
test linux x86-64 2/8	11m 50s
test linux x86-64 3/8	12m 53s
test linux x86-64 4/8	8m 48s
test linux x86-64 5/8	8m 10s
test linux x86-64 6/8	6m 34s
test linux x86-64 7/8	6m 38s
test linux x86-64 8/8	4m 50s
test windows x86-64 1/8	8m 37s
test windows x86-64 2/8	11m 24s
test windows x86-64 3/8	11m 25s
test windows x86-64 4/8	8m 30s
test windows x86-64 5/8	8m 12s
test windows x86-64 6/8	6m 9s
test windows x86-64 7/8	6m 21s
test windows x86-64 8/8	4m 46s
	2h 35m 26s

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