ffi: fix compilation errors #111

Job	Run time
quiche	3m 32s
quiche_ios (x86_64-apple-ios)	1m 17s
quiche (boringssl-boring-crate)	3m 31s
http3_test	49s
quiche_ios (aarch64-apple-ios)	1m 34s
quiche (openssl)	6m 8s
quiche_macos (macos-13)	3m 45s
quiche_multiarch (aarch64-unknown-linux-gnu)	2m 49s
quiche_macos (macos-latest)	2m 18s
quiche_windows (x86_64-pc-windows-msvc)	6m 57s
quiche_multiarch (armv7-unknown-linux-gnueabihf)	3m 6s
quiche_windows (i686-pc-windows-msvc)	4m 0s
quiche_multiarch (i686-unknown-linux-gnu)	1m 30s
quiche_windows (x86_64-pc-windows-gnu)	6m 13s
quiche_windows (i686-pc-windows-gnu)	6m 29s
android_ndk_lts (aarch64-linux-android)	1m 8s
android_ndk_lts (armv7-linux-androideabi)	59s
android_ndk_lts (x86_64-linux-android)	58s
docker	3m 15s
android_ndk_lts (i686-linux-android)	1m 10s
nginx (1.16.1)	50s
	1h 2m 18s

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