Remove duplicated ANDROID_PLATFORM and define in CMake (#6223) #4636

Job	Run time
build-benchmark-app / macos-job	23m 22s
build-frameworks-ios / macos-job	28m 18s
build-demo-ios / macos-job	12m 35s
upload-demo-ios	19s
test-demo-ios / mobile-job (ios)	15m 34s
upload-frameworks-ios	21s
	1h 20m 29s

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