avoid panic/unwind on extern "C" fnc #951

Job	Run time
Build (x86_64-pc-windows-msvc)	7m 7s
Build (aarch64-pc-windows-msvc)	6m 17s
Build (x86_64-apple-darwin)	8m 7s
Build (aarch64-apple-darwin)	8m 58s
Build (aarch64-apple-ios)	8m 23s
Build (aarch64-apple-ios-sim)	9m 4s
Build (x86_64-unknown-linux-gnu)	3m 26s
Build (aarch64-unknown-linux-gnu)	5m 12s
Build (aarch64-linux-android)	3m 50s
Build (armv7-linux-androideabi)	3m 47s
Build (x86_64-linux-android)	3m 35s
	1h 7m 46s

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