Add `DefinedMacros` handler #7598

Job	Run time
build test linux x86-64	3m 38s
build test windows x86-64	8m 59s
check-rust	3m 37s
check-website	13s
scarb-metadata compatibility check	40s
doc tests	3m 2s
test linux x86-64 1/8	15m 48s
test linux x86-64 2/8	17m 19s
test linux x86-64 3/8	13m 56s
test linux x86-64 4/8	13m 17s
test linux x86-64 5/8	11m 26s
test linux x86-64 6/8	9m 34s
test linux x86-64 7/8	9m 38s
test linux x86-64 8/8	10m 53s
test windows x86-64 1/8	14m 27s
test windows x86-64 2/8	15m 18s
test windows x86-64 3/8	13m 57s
test windows x86-64 4/8	12m 33s
test windows x86-64 5/8	12m 10s
test windows x86-64 6/8	9m 25s
test windows x86-64 7/8	9m 35s
test windows x86-64 8/8	10m 3s
	3h 39m 28s

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