CMake

dnn/download_model.sh: Try shasum if no sha256sum #1099

Job	Run time
CMake MINGW	1m 7s
Test build with CMake 3.16.0	1m 24s
CMake/Android/So/X86/Release	31s
CMake/Windows/Dll/X64/Release	1m 12s
CMake/Windows/Dll/ARMv8/Release	1m 3s
CMake/Android/So/ARMv8/Release	44s
CMake/Windows/Dll/X86/Release	1m 8s
CMake/Android/So/X64/Release	44s
CMake/MacOSX/Framework/X64/Release	1m 31s
CMake/Windows/Lib/armv8/Release	57s
CMake/Linux/Lib/X64/Release	1m 24s
CMake/MacOSX/So/X64/Release	35s
CMake/iOS/Framework/arm64/Release	52s
CMake/iOS/Lib/arm64/Release	51s
CMake/iOS/Dll/arm64/Release	59s
CMake/Android/Lib/X86/Release	36s
CMake/Windows/Lib/X64/Release	3m 3s
CMake/Windows/Lib/X86/Release	2m 43s
CMake/CustomModes/Linux/Lib/X64/Release	1m 18s
CMake/Linux/So/X64/Release	34s
CMake/AssertionsFuzz/Linux/Lib/X64/Release	1m 22s
CMake/Android/Lib/X64/Release	35s
CMake/AssertionsFuzz/Windows/Lib/X64/Release	2m 31s
CMake/AssertionsFuzz/MacOSX/Lib/X64/Release	1m 39s
CMake/Android/Lib/ARMv8/Release	36s
CMake/MacOSX/Lib/X64/Release	1m 35s
	31m 34s

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