feat(bob): support custom target definitions #918

Job	Run time
build (macos, fabric-view, kotlin-objc)	1m 43s
build (macos, legacy-module, cpp)	1m 57s
build (macos, legacy-module, kotlin-swift)	2m 1s
build (macos, legacy-module, kotlin-objc)	2m 2s
build (macos, legacy-view, kotlin-swift)	2m 7s
build (macos, legacy-view, kotlin-objc)	2m 2s
build (macos, turbo-module, cpp)	1m 43s
build (macos, turbo-module, kotlin-objc)	1m 52s
build (ubuntu, fabric-view, kotlin-objc)	1m 53s
build (ubuntu, legacy-module, cpp)	1m 43s
build (ubuntu, legacy-module, kotlin-swift)	1m 22s
build (ubuntu, legacy-module, kotlin-objc)	1m 26s
build (ubuntu, legacy-view, kotlin-swift)	1m 39s
build (ubuntu, legacy-view, kotlin-objc)	1m 35s
build (ubuntu, library, js)	1m 34s
build (ubuntu, turbo-module, cpp)	1m 25s
build (ubuntu, turbo-module, kotlin-objc)	1m 27s
	29m 31s

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